How we think about browsers

At GitHub, we believe it’s not fully shipped until it’s fast. JavaScript makes a big impact on how pages perform. One way we work to improve JavaScript performance is to make changes to the native syntax and polyfills we ship. For example, in January of this year, we updated our compiler to output native ES2019 code, shipping native syntax for optional catch binding.

JavaScript doesn’t get executed on very old browsers when native syntax for new language features is encountered. However, thanks to GitHub being built following the principle of progressive enhancement, users of older browsers still get to interact with basic features of GitHub, while users with more capable browsers get a faster experience.

GitHub will soon be serving JavaScript using syntax features found in the ECMAScript 2020 standard, which includes the optional chaining and nullish coalescing operators. This change will lead to a 10kb reduction in JavaScript across the site.

We want to take this opportunity to go into detail about how we think about browser support. We will share data about our customers’ browser usage patterns and introduce you to some of the tools we use to make sure our customers are getting the best experience, including our recently open-sourced browser support library.

What browsers do our customers use?

To monitor the performance of pages, we collect some usage information. We parse User-Agent headers as part of our analytics, which lets us make informed decisions based on the browsers our users are running. Some of these decisions include, what browsers we execute automated tests on, the configuration of our static analysis tools, and even what features we ship. Around 95% of requests to our web services come from browsers with an identifying user agent string. Another 1% of requests have no User-Agent header, and the remaining 4% make up scripts, like Python (2%) or programs like cURL (0.5%).

We encourage users to use the latest versions of Chrome, Edge, Firefox, or Safari, and our data shows that a majority of users do so. Here’s what the browser market share looked like for visits to github.com between May 9-13, 2022:

	Beta	Latest	-1	-2	-3	-4	-5	-6	-7	-8	Total
Chrome	0.2950%	53.0551%	12.7103%	1.8120%	0.8076%	0.4737%	0.5504%	0.1728%	0.1677%	0.1029%	70.1478%
Edge	0.0000%	6.3404%	0.5328%	0.0978%	0.0432%	0.0202%	0.0143%	0.0063%	0.0058%	0.0046%	7.0657%
Firefox	0.6525%	7.7374%	2.9717%	0.2243%	0.1041%	0.1018%	0.0541%	0.0396%	0.0219%	0.0172%	11.9249%
Safari	0.0000%	2.8802%	0.7049%	0.2110%	0.0000%	0.3288%	0.0000%	0.0696%	0.0000%	0.0094%	4.2038%
Opera	0.0030%	0.2650%	1.1173%	0.0112%	0.0044%	0.0043%	0.0016%	0.0017%	0.0015%	0.0011%	1.4112%
Internet Explorer	0.0000%	0.0658%	0.0001%	0.0001%	0.0000%	0.0000%	0.0001%	0.0000%	0.0000%	0.0000%	0.0662%
Samsung Internet	0.0000%	0.0276%	0.0007%	0.0012%	0.0008%	0.0000%	0.0000%	0.0000%	0.0000%	0.0000%	0.0302%
Total	0.9507%	70.3716%	18.0379%	2.3576%	0.9602%	0.9289%	0.6207%	0.2901%	0.1968%	0.1352%	94.8498%

The above graph shows two dimensions: market share across browser vendors, and market share across versions. Looking at traffic with a branded user-agent string shows that roughly 95% of requests are coming from one of seven browsers. It also shows us that—perhaps unsurprisingly—the majority of requests come from Google Chrome (more than 70%), 12% from Firefox, 7% from Edge, 4.2% from Safari, and 1.4% from Opera (all other browser vendors represent significantly less than 1% of traffic).

The fall-off for outdated versions of browsers is very steep. While over 70% of requests come from the latest release of a browser, 18% come from the previous release. Requests coming from three versions behind the latest fall to less than 1%. These numbers tell us that we can make the most impact by concentrating on Chrome, Firefox, Edge, and Safari, in that order. That’s not the whole story, though. Another vector to look at is over time:

	15.4	15.3	15.2	15.1	15.0	14.1	14.0	13.1	13.0	12.1	12.0	<12
2022-01-01	0.2130%	1.9933%	31.9792%	25.3472%	6.1477%	11.5005%	3.9045%	2.3446%	0.5210%	0.9379%	0.0336%	15.0773%
2022-01-02	0.2548%	2.0334%	32.8731%	25.9360%	6.4715%	12.0837%	3.7401%	2.4652%	0.5292%	0.8598%	0.0297%	12.7235%
2022-01-03	0.3078%	1.6285%	34.9256%	27.0666%	7.3738%	13.7125%	3.7582%	2.1204%	0.4217%	0.6152%	0.0238%	8.0459%
2022-01-04	0.3637%	1.4860%	35.6528%	26.9236%	7.6980%	14.2046%	3.6510%	2.0938%	0.3804%	0.5613%	0.0305%	6.9543%
2022-01-05	0.3519%	1.4723%	35.8533%	26.3673%	7.6227%	14.5006%	3.7131%	2.1403%	0.3793%	0.5682%	0.0254%	7.0055%
2022-01-06	0.3575%	1.5431%	36.6670%	25.8058%	7.5075%	14.2149%	3.7570%	2.1580%	0.3888%	0.6040%	0.0242%	6.9722%
2022-01-07	0.4123%	1.6277%	37.4426%	25.2663%	7.3924%	13.8618%	3.6753%	2.0874%	0.4024%	0.5904%	0.0270%	7.2144%
2022-01-08	0.3237%	1.9625%	35.9640%	24.3500%	6.2977%	12.0691%	3.7139%	2.3841%	0.5170%	0.8028%	0.0266%	11.5885%
2022-01-09	0.2964%	1.9599%	36.0700%	24.2496%	6.3270%	12.0979%	3.7857%	2.3146%	0.4816%	0.8567%	0.0242%	11.5363%
2022-01-10	0.3488%	1.5101%	39.0599%	24.5018%	7.2861%	14.0757%	3.6064%	2.0192%	0.3818%	0.5383%	0.0285%	6.6433%
2022-01-11	0.4108%	1.5541%	39.4265%	24.3465%	7.3778%	14.1840%	3.5905%	1.9870%	0.3366%	0.5555%	0.0253%	6.2052%
2022-01-12	0.3743%	1.5182%	40.0054%	23.9508%	7.3054%	14.1456%	3.5695%	2.0163%	0.3643%	0.5105%	0.0308%	6.2090%
2022-01-13	0.3380%	1.5659%	40.3951%	23.5803%	7.2104%	14.1495%	3.6099%	1.9705%	0.3716%	0.5117%	0.0229%	6.2743%
2022-01-14	0.3709%	1.6172%	40.8321%	23.4113%	6.9690%	13.5323%	3.5354%	1.9806%	0.3559%	0.5424%	0.0251%	6.8279%
2022-01-15	0.2870%	2.0547%	39.7351%	22.0067%	5.9847%	11.7234%	3.6011%	2.2909%	0.4668%	0.7720%	0.0287%	11.0489%
2022-01-16	0.2964%	2.0923%	40.8441%	20.6853%	5.9118%	11.8049%	3.6625%	2.3851%	0.4599%	0.8312%	0.0294%	10.9970%
2022-01-17	0.3043%	1.6554%	43.8724%	20.6116%	6.6334%	13.7081%	3.5519%	2.0195%	0.3721%	0.5356%	0.0287%	6.7071%
2022-01-18	0.3448%	1.5978%	45.3308%	19.6763%	6.7137%	13.6977%	3.5498%	1.9990%	0.3478%	0.5166%	0.0289%	6.1968%
2022-01-19	0.3490%	1.6179%	46.3810%	19.0037%	6.5909%	13.7031%	3.4676%	1.9497%	0.3358%	0.4847%	0.0264%	6.0901%
2022-01-20	0.3410%	1.6362%	47.2639%	18.3797%	6.4656%	13.3978%	3.3907%	1.9803%	0.3393%	0.5244%	0.0245%	6.2566%
2022-01-21	0.3553%	1.7170%	48.0184%	17.4454%	6.3012%	13.1411%	3.3914%	2.0109%	0.3696%	0.4934%	0.0230%	6.7332%
2022-01-22	0.2929%	2.3538%	46.1479%	16.4726%	5.4806%	11.2732%	3.4515%	2.1378%	0.4547%	0.7435%	0.0291%	11.1624%
2022-01-23	0.2595%	2.3385%	47.0822%	15.5800%	5.4940%	11.0466%	3.5465%	2.2365%	0.4565%	0.7749%	0.0233%	11.1614%
2022-01-24	0.3607%	1.7504%	50.7307%	15.3784%	6.1093%	12.9047%	3.4166%	2.0184%	0.3442%	0.4872%	0.0225%	6.4769%
2022-01-25	0.3654%	1.7706%	51.9246%	14.6195%	6.0739%	12.9834%	3.3441%	1.9226%	0.3283%	0.4742%	0.0197%	6.1736%
2022-01-26	0.3465%	2.1688%	52.4595%	14.0287%	5.9250%	12.4463%	3.3065%	1.9205%	0.3530%	0.5013%	0.0244%	6.5195%
2022-01-27	0.3628%	7.7522%	47.3489%	13.5902%	5.8790%	12.5425%	3.2687%	1.9584%	0.3513%	0.4820%	0.0285%	6.4356%
2022-01-28	0.8512%	12.2593%	43.2173%	12.7719%	5.7684%	12.2779%	3.2807%	1.8948%	0.3661%	0.4896%	0.0249%	6.7981%
2022-01-29	1.5324%	15.5746%	37.9759%	11.4900%	5.0904%	10.8157%	3.2414%	2.2146%	0.4751%	0.7246%	0.0226%	10.8425%
2022-01-30	1.8095%	17.1024%	36.5444%	11.5112%	5.0038%	10.5058%	3.3404%	2.2842%	0.4604%	0.7569%	0.0187%	10.6623%
2022-01-31	1.5814%	17.6461%	38.7703%	12.5933%	5.6880%	12.0274%	3.1897%	1.8416%	0.3408%	0.4923%	0.0240%	5.8050%
2022-02-01	1.7441%	19.2814%	37.2947%	12.3450%	5.5508%	11.9390%	3.1856%	1.8109%	0.3369%	0.4689%	0.0228%	6.0199%
2022-02-02	1.8425%	20.6234%	36.1439%	12.2229%	5.5517%	11.8100%	3.0868%	1.7966%	0.3369%	0.4872%	0.0285%	6.0697%
2022-02-03	1.8914%	21.5787%	34.9534%	12.0932%	5.4199%	11.7927%	3.1686%	1.8609%	0.3504%	0.4656%	0.0240%	6.4013%
2022-02-04	1.9648%	22.7768%	34.0393%	11.7468%	5.2886%	11.4763%	3.0458%	1.8618%	0.3508%	0.5207%	0.0221%	6.9061%
2022-02-05	2.3963%	23.4144%	30.8252%	10.7756%	4.6826%	10.0675%	3.2277%	2.1561%	0.4480%	0.7145%	0.0214%	11.2706%
2022-02-06	2.3912%	24.0953%	30.5678%	10.4257%	4.7046%	10.0236%	3.3234%	2.1215%	0.4327%	0.7056%	0.0193%	11.1893%
2022-02-07	2.0336%	24.6938%	32.2185%	11.5380%	5.1985%	11.8112%	3.1986%	1.9324%	0.3535%	0.4776%	0.0249%	6.5194%
2022-02-08	2.0578%	25.5825%	31.5513%	11.4319%	5.1997%	11.8368%	3.1809%	1.8839%	0.3255%	0.4600%	0.0220%	6.4678%
2022-02-09	2.1357%	26.4126%	31.2722%	11.3999%	5.2737%	11.9741%	3.1823%	1.9032%	0.2298%	0.2883%	0.0204%	5.9077%
2022-02-10	2.1586%	27.2403%	30.8552%	11.3862%	5.2045%	11.8815%	3.1880%	1.5341%	0.2342%	0.2931%	0.0234%	6.0009%
2022-02-11	2.3263%	28.7838%	30.1344%	11.3683%	5.1761%	11.6652%	3.1655%	0.8880%	0.1781%	0.2133%	0.0214%	6.0796%
2022-02-12	2.7622%	28.4764%	26.9469%	9.7973%	4.4372%	9.9020%	3.1473%	2.1256%	0.4193%	0.7154%	0.0241%	11.2464%
2022-02-13	2.6300%	28.9074%	26.5648%	9.9005%	4.4070%	9.9237%	3.1472%	2.2069%	0.4375%	0.7176%	0.0234%	11.1339%
2022-02-14	2.2108%	30.1253%	28.0680%	10.8367%	5.0225%	11.6307%	3.1060%	1.7727%	0.3190%	0.4699%	0.0230%	6.4155%
2022-02-15	2.2626%	31.0756%	27.6637%	10.8023%	4.9224%	11.5579%	3.0697%	1.7311%	0.3060%	0.4568%	0.0263%	6.1257%
2022-02-16	2.3030%	31.5893%	27.2155%	10.7267%	4.8788%	11.4932%	2.9605%	1.7814%	0.3026%	0.4668%	0.0264%	6.2558%
2022-02-17	2.3139%	32.1564%	26.7888%	10.6523%	4.7749%	11.4135%	3.0497%	1.8037%	0.3309%	0.4543%	0.0254%	6.2362%
2022-02-18	2.3419%	33.8505%	25.1471%	10.3232%	4.6872%	11.2973%	2.9507%	1.8080%	0.3524%	0.4658%	0.0234%	6.7524%
2022-02-19	2.8255%	35.4968%	21.2425%	9.0705%	4.3585%	9.6129%	3.0839%	2.1391%	0.4321%	0.7214%	0.0240%	10.9927%
2022-02-20	2.7597%	37.2786%	19.6970%	9.0995%	4.3411%	9.6230%	3.0634%	2.1577%	0.4466%	0.6930%	0.0223%	10.8180%
2022-02-21	2.2972%	39.5270%	20.2617%	9.8308%	4.5785%	11.0922%	3.0427%	1.8432%	0.3359%	0.4971%	0.0203%	6.6735%
2022-02-22	2.3285%	41.6072%	18.8362%	9.5382%	4.5626%	11.1426%	3.0037%	1.8037%	0.3116%	0.4570%	0.0206%	6.3882%
2022-02-23	2.3564%	42.9442%	17.7843%	9.3653%	4.5609%	11.0347%	2.8992%	1.7738%	0.3189%	0.4421%	0.0198%	6.5005%
2022-02-24	2.3331%	43.8819%	16.9144%	9.1178%	4.5580%	11.1665%	2.9641%	1.7680%	0.3063%	0.4369%	0.0224%	6.5306%
2022-02-25	2.3644%	45.0140%	15.8175%	8.8273%	4.4317%	10.9711%	2.9355%	1.7624%	0.3324%	0.4556%	0.0238%	7.0641%
2022-02-26	2.9596%	44.4252%	13.1945%	7.6195%	3.9776%	9.4234%	3.1355%	2.0300%	0.5206%	0.7039%	0.0223%	11.9878%
2022-02-27	2.8501%	45.0292%	12.5025%	7.7242%	4.0507%	9.4992%	3.0954%	2.1008%	0.4980%	0.6989%	0.0251%	11.9258%
2022-02-28	2.3807%	47.0753%	14.2634%	8.4807%	4.2220%	10.9576%	3.0524%	1.8148%	0.3434%	0.4632%	0.0242%	6.9222%
2022-03-01	2.3748%	48.2034%	13.7801%	8.3157%	4.2605%	10.7307%	2.9418%	1.8095%	0.3259%	0.4437%	0.0224%	6.7913%
2022-03-02	2.3629%	48.7995%	13.5339%	8.1894%	4.2284%	10.7893%	2.9092%	1.7475%	0.3293%	0.4560%	0.0220%	6.6327%
2022-03-03	2.4486%	49.7154%	12.6928%	8.1700%	4.1801%	10.6387%	2.8873%	1.7340%	0.3109%	0.4497%	0.0246%	6.7479%
2022-03-04	2.5373%	50.2026%	12.4981%	7.7686%	4.1271%	10.5053%	2.8372%	1.7236%	0.3080%	0.4493%	0.0255%	7.0174%
2022-03-05	3.0231%	49.3317%	10.5426%	6.5147%	3.7707%	9.0290%	3.0784%	2.0464%	0.4182%	0.6288%	0.0208%	11.5956%
2022-03-06	3.0723%	49.6284%	10.0200%	6.7391%	3.7704%	9.0282%	3.0924%	2.1063%	0.4288%	0.6881%	0.0213%	11.4046%
2022-03-07	2.4667%	51.7157%	11.7176%	7.6974%	4.1000%	10.2989%	2.8448%	1.7253%	0.3185%	0.4412%	0.0236%	6.6503%
2022-03-08	2.4190%	52.4292%	11.3917%	7.3946%	4.1027%	10.3559%	2.8335%	1.7378%	0.3259%	0.4500%	0.0230%	6.5368%
2022-03-09	2.4744%	52.9758%	11.0708%	7.4840%	4.0474%	10.3307%	2.8409%	1.6682%	0.3015%	0.4183%	0.0210%	6.3667%
2022-03-10	2.5404%	53.2418%	10.8388%	7.3800%	3.9569%	10.2019%	2.8462%	1.7425%	0.3027%	0.4212%	0.0254%	6.5022%
2022-03-11	2.6346%	53.8851%	10.3123%	7.1008%	3.8969%	9.8746%	2.7686%	1.6714%	0.2988%	0.4224%	0.0252%	7.1092%
2022-03-12	3.2418%	52.4146%	8.4171%	6.0948%	3.5575%	8.6494%	3.0048%	2.0180%	0.3927%	0.7005%	0.0251%	11.4838%
2022-03-13	3.2069%	52.3926%	8.5002%	6.1721%	3.5239%	8.4507%	2.9757%	2.1148%	0.3755%	0.7167%	0.0254%	11.5456%
2022-03-14	3.2185%	54.3662%	9.8584%	7.0464%	3.8492%	9.8257%	2.7413%	1.6965%	0.2680%	0.4273%	0.0270%	6.6756%
2022-03-15	11.1192%	47.4059%	9.5438%	6.8719%	3.7611%	9.7005%	2.7719%	1.6308%	0.2637%	0.4211%	0.0250%	6.4849%
2022-03-16	17.9069%	41.3967%	9.1987%	6.6590%	3.7184%	9.5772%	2.6822%	1.6273%	0.2877%	0.4349%	0.0197%	6.4914%
2022-03-17	21.7348%	38.1323%	8.8607%	6.5819%	3.6503%	9.4056%	2.6279%	1.6295%	0.2814%	0.4449%	0.0250%	6.6258%
2022-03-18	24.4165%	35.7041%	8.5482%	6.3399%	3.5433%	9.0851%	2.5852%	1.6362%	0.2685%	0.4610%	0.0258%	7.3863%
2022-03-19	26.2368%	31.9489%	6.8779%	5.5836%	3.3195%	7.9382%	2.7793%	1.9717%	0.3594%	0.6485%	0.0219%	12.3144%
2022-03-20	27.3687%	30.7753%	7.0252%	5.5489%	3.3195%	7.9491%	2.8717%	1.9881%	0.3587%	0.6629%	0.0231%	12.1088%
2022-03-21	28.2620%	32.3271%	8.3673%	6.3448%	3.4783%	9.2887%	2.6006%	1.6620%	0.2865%	0.4242%	0.0238%	6.9347%
2022-03-22	29.5670%	31.4166%	8.2768%	6.3061%	3.4969%	9.2905%	2.5700%	1.5872%	0.2591%	0.4296%	0.0227%	6.7774%
2022-03-23	30.6539%	30.6544%	8.0608%	6.2326%	3.4798%	9.1248%	2.5844%	1.6372%	0.2534%	0.4191%	0.0235%	6.8761%
2022-03-24	32.0481%	29.9540%	8.0759%	6.0714%	3.4595%	9.0259%	2.5544%	1.5634%	0.2705%	0.4064%	0.0225%	6.5478%
2022-03-25	32.7566%	28.9962%	7.7413%	5.9692%	3.3709%	8.7142%	2.5446%	1.5842%	0.2667%	0.4180%	0.0235%	7.6147%
2022-03-26	32.5970%	26.7095%	6.2462%	5.0950%	3.2226%	7.6540%	2.7770%	1.8228%	0.3847%	0.6553%	0.0210%	12.8149%
2022-03-27	33.0257%	26.3003%	6.3665%	5.3195%	3.2245%	7.8100%	2.8208%	1.8248%	0.3827%	0.6404%	0.0235%	12.2614%
2022-03-28	34.6919%	27.5399%	7.6902%	5.9742%	3.3578%	8.8958%	2.5193%	1.6230%	0.2658%	0.3997%	0.0232%	7.0192%
2022-03-29	35.6580%	27.0895%	7.6128%	5.9695%	3.3326%	8.7237%	2.4484%	1.5631%	0.2741%	0.3802%	0.0223%	6.9258%
2022-03-30	36.0933%	26.8011%	7.4668%	5.9183%	3.3682%	8.6179%	2.4670%	1.5698%	0.2556%	0.4017%	0.0195%	7.0208%
2022-03-31	36.7627%	26.3586%	7.4152%	5.8338%	3.2992%	8.6070%	2.5025%	1.5928%	0.2742%	0.4120%	0.0184%	6.9235%
2022-04-01	37.7935%	25.6391%	7.0944%	5.6951%	3.3207%	8.4395%	2.3936%	1.5895%	0.2895%	0.4032%	0.0177%	7.3242%
2022-04-02	36.7583%	23.8424%	6.0495%	4.9378%	3.1161%	7.6109%	2.7326%	1.8943%	0.3616%	0.6358%	0.0209%	12.0398%
2022-04-03	38.0555%	23.4329%	5.9867%	5.0717%	3.1091%	7.4917%	2.6295%	1.8512%	0.3456%	0.6151%	0.0185%	11.3926%
2022-04-04	39.5734%	24.4753%	7.2343%	5.6909%	3.1580%	8.4157%	2.4270%	1.5334%	0.2433%	0.4101%	0.0237%	6.8149%
2022-04-05	40.1999%	24.3237%	7.1533%	5.5920%	3.2204%	8.3465%	2.3998%	1.4640%	0.2627%	0.3814%	0.0251%	6.6309%
2022-04-06	40.3972%	23.9005%	7.0750%	5.5978%	3.4175%	8.4546%	2.3345%	1.5084%	0.2411%	0.4040%	0.0226%	6.6467%
2022-04-07	40.6483%	23.5724%	6.9376%	5.5906%	3.5983%	8.4082%	2.3696%	1.5432%	0.2714%	0.3932%	0.0221%	6.6452%
2022-04-08	41.0291%	23.0447%	6.7669%	5.3345%	3.7167%	8.1355%	2.3707%	1.5204%	0.2979%	0.4360%	0.0227%	7.3250%
2022-04-09	39.0096%	21.5707%	5.5139%	4.6910%	3.8459%	7.1101%	2.6170%	1.8408%	0.3681%	0.6555%	0.0163%	12.7611%
2022-04-10	38.9654%	21.5612%	5.7157%	4.7531%	3.9948%	7.0060%	2.6146%	1.9593%	0.3643%	0.6320%	0.0189%	12.4146%
2022-04-11	41.7134%	22.3259%	6.8796%	5.4925%	3.8380%	8.2313%	2.3455%	1.5951%	0.2604%	0.3967%	0.0202%	6.9013%
2022-04-12	42.9776%	21.4756%	6.6304%	5.3460%	3.9136%	8.1430%	2.3224%	1.4970%	0.2704%	0.4073%	0.0232%	6.9935%
2022-04-13	44.8529%	19.5508%	6.5201%	5.2781%	3.9081%	8.1321%	2.3117%	1.4651%	0.2597%	0.3798%	0.0203%	7.3213%
2022-04-14	47.2604%	18.5562%	6.3329%	5.0969%	3.9568%	7.8447%	2.2326%	1.4409%	0.2660%	0.3694%	0.0195%	6.6238%
2022-04-15	46.1738%	17.2112%	5.7005%	4.8802%	4.1301%	7.6028%	2.4450%	1.5947%	0.3140%	0.4888%	0.0221%	9.4369%
2022-04-16	45.0816%	15.9900%	4.9427%	4.2670%	4.3097%	6.9089%	2.5115%	1.7646%	0.3776%	0.6567%	0.0196%	13.1700%
2022-04-17	45.9303%	15.1178%	4.8665%	4.3033%	4.3275%	6.9231%	2.6406%	1.7807%	0.3541%	0.6456%	0.0216%	13.0890%
2022-04-18	48.5945%	15.2044%	5.8556%	4.8611%	4.2658%	7.9850%	2.4404%	1.6419%	0.2887%	0.4655%	0.0209%	8.3763%
2022-04-19	50.8857%	14.9250%	5.8652%	5.0294%	3.9808%	7.8429%	2.2999%	1.4581%	0.2670%	0.3945%	0.0178%	7.0337%
2022-04-20	51.9700%	14.2590%	5.8156%	4.8890%	4.0109%	7.6977%	2.2176%	1.4981%	0.2546%	0.4005%	0.0209%	6.9662%
2022-04-21	52.5838%	13.5549%	5.7156%	4.8685%	3.9548%	7.6767%	2.3164%	1.4839%	0.2606%	0.4122%	0.0211%	7.1515%
2022-04-22	53.0145%	12.8874%	5.4692%	4.7749%	4.0399%	7.5126%	2.2910%	1.4816%	0.2738%	0.3989%	0.0203%	7.8361%
2022-04-23	51.2057%	11.0804%	4.4180%	4.1472%	4.4620%	6.6022%	2.4416%	1.8031%	0.3768%	0.5984%	0.0245%	12.8400%
2022-04-24	51.2867%	10.9186%	4.6488%	4.1452%	4.2797%	6.9482%	2.6263%	1.8961%	0.3964%	0.6026%	0.0243%	12.2271%
2022-04-25	54.1650%	12.3169%	5.5367%	4.7520%	4.0855%	7.5898%	2.2639%	1.4719%	0.2677%	0.4090%	0.0216%	7.1201%
2022-04-26	55.1848%	11.9726%	5.3847%	4.6786%	4.0406%	7.4071%	2.2462%	1.4609%	0.2643%	0.3727%	0.0237%	6.9636%
2022-04-27	55.9856%	11.5124%	5.3171%	4.5683%	3.9992%	7.3195%	2.2536%	1.4565%	0.2617%	0.3671%	0.0254%	6.9336%
2022-04-28	56.1709%	11.2112%	5.3278%	4.5597%	4.0453%	7.2469%	2.1800%	1.4478%	0.2588%	0.3927%	0.0223%	7.1366%
2022-04-29	56.4630%	10.8456%	5.0356%	4.3545%	4.1464%	7.2195%	2.1173%	1.4117%	0.2479%	0.4089%	0.0203%	7.7295%
2022-04-30	53.9976%	8.9824%	4.1147%	3.7867%	4.3880%	6.3945%	2.5134%	1.7417%	0.3505%	0.6254%	0.0265%	13.0786%

Safari releases a major version each year alongside macOS and iOS. The above shows the release cadence from January-April for Safari traffic on GitHub.com. While we see older versions used quite heavily, we also see regular upgrade cadence from Safari users, especially 15.x releases, with peak-to-peak usage approximately every eight weeks.

	101	100	99	98	97	96	<90	95	94	93	92	91	90
2022-01-01	0.0000%	0.3491%	0.1468%	0.2108%	0.3386%	86.6783%	5.1358%	2.2244%	1.7838%	0.5934%	1.5257%	0.5474%	0.4658%
2022-01-02	0.0000%	0.3455%	0.1363%	0.1842%	0.3181%	88.7497%	3.2558%	2.2186%	1.8004%	0.5739%	1.4336%	0.5302%	0.4538%
2022-01-03	0.0000%	0.2731%	0.0937%	0.1450%	0.2434%	90.4934%	2.1269%	2.5113%	1.5836%	0.5793%	1.0352%	0.5289%	0.3861%
2022-01-04	0.0000%	0.2561%	0.0908%	0.1459%	0.2757%	90.3926%	2.2204%	2.5350%	1.5445%	0.5799%	1.0151%	0.5280%	0.4160%
2022-01-05	0.0000%	0.2556%	0.0899%	0.1520%	4.1497%	86.6672%	2.2260%	2.4636%	1.5101%	0.5757%	0.9840%	0.5220%	0.4042%
2022-01-06	0.0000%	0.2508%	0.0815%	0.1412%	10.7723%	80.2589%	2.1902%	2.3842%	1.4689%	0.5581%	0.9913%	0.5089%	0.3937%
2022-01-07	0.0000%	0.1932%	0.0962%	0.1629%	21.5610%	69.5394%	2.2636%	2.2909%	1.4494%	0.5384%	1.0015%	0.5018%	0.4017%
2022-01-08	0.0000%	0.1744%	0.1480%	0.2586%	33.5510%	56.3914%	2.9587%	2.0026%	1.7096%	0.5449%	1.3334%	0.5045%	0.4230%
2022-01-09	0.0000%	0.1518%	0.1521%	0.2564%	37.8032%	52.5723%	2.8295%	1.8732%	1.6458%	0.5064%	1.3001%	0.4884%	0.4208%
2022-01-10	0.0000%	0.1330%	0.1059%	0.1782%	36.7369%	54.4084%	2.4167%	2.1394%	1.4727%	0.5493%	0.9584%	0.5085%	0.3927%
2022-01-11	0.0000%	0.1219%	0.1051%	0.2332%	45.4664%	46.0626%	2.2293%	2.0457%	1.4169%	0.5245%	0.9212%	0.4878%	0.3853%
2022-01-12	0.0000%	0.1134%	0.1468%	0.2459%	57.1392%	34.5425%	2.1934%	1.9506%	1.3772%	0.5162%	0.9154%	0.4807%	0.3786%
2022-01-13	0.0000%	0.1046%	0.1624%	0.2693%	65.4838%	26.4436%	2.0266%	1.8866%	1.3646%	0.4987%	0.9004%	0.4861%	0.3733%
2022-01-14	0.0000%	0.1031%	0.1829%	0.3063%	70.0467%	21.6414%	2.2699%	1.8110%	1.3665%	0.4882%	0.9326%	0.4758%	0.3755%
2022-01-15	0.0000%	0.1537%	0.2627%	0.4051%	74.7938%	15.8317%	2.8385%	1.6009%	1.5320%	0.4885%	1.2465%	0.4664%	0.3802%
2022-01-16	0.0000%	0.1602%	0.2558%	0.3909%	76.5597%	14.3898%	2.7115%	1.5114%	1.5108%	0.4653%	1.2131%	0.4474%	0.3840%
2022-01-17	0.0000%	0.1317%	0.1893%	0.2867%	76.2164%	15.8049%	2.0853%	1.6876%	1.3236%	0.4815%	0.9184%	0.4969%	0.3777%
2022-01-18	0.0000%	0.1289%	0.1898%	0.2709%	77.6409%	14.7878%	1.9411%	1.6397%	1.2295%	0.4692%	0.8660%	0.4755%	0.3606%
2022-01-19	0.0000%	0.1319%	0.1909%	0.2707%	79.0723%	13.6180%	1.9163%	1.5781%	1.0862%	0.4649%	0.8503%	0.4634%	0.3568%
2022-01-20	0.0000%	0.1221%	0.1687%	0.2831%	80.3988%	12.5592%	1.8927%	1.4921%	1.0036%	0.4499%	0.8351%	0.4446%	0.3500%
2022-01-21	0.0000%	0.1234%	0.1599%	0.2858%	81.4219%	11.6477%	1.9316%	1.3819%	0.9494%	0.4453%	0.8615%	0.4436%	0.3480%
2022-01-22	0.0000%	0.1797%	0.2379%	0.3808%	82.0847%	9.9598%	2.6312%	1.2211%	0.9332%	0.4429%	1.1404%	0.4392%	0.3493%
2022-01-23	0.0000%	0.1942%	0.2317%	0.3695%	82.6698%	9.5777%	2.5169%	1.1724%	0.9056%	0.4432%	1.1244%	0.4327%	0.3617%
2022-01-24	0.0000%	0.1529%	0.1677%	0.2628%	83.1674%	10.2728%	1.8032%	1.2686%	0.8822%	0.4320%	0.8178%	0.4349%	0.3377%
2022-01-25	0.0000%	0.1588%	0.1748%	0.2607%	83.9039%	9.7041%	1.7497%	1.2257%	0.8594%	0.4230%	0.7947%	0.4221%	0.3230%
2022-01-26	0.0000%	0.1649%	0.1919%	0.2684%	84.5595%	9.1948%	1.7411%	1.1326%	0.8188%	0.4088%	0.7871%	0.4108%	0.3213%
2022-01-27	0.0000%	0.1706%	0.1723%	0.2653%	85.0102%	8.7534%	1.7195%	1.1492%	0.8218%	0.4177%	0.7826%	0.4201%	0.3175%
2022-01-28	0.0000%	0.1863%	0.1721%	0.2998%	85.4656%	8.3345%	1.7354%	1.1011%	0.7879%	0.4023%	0.7755%	0.4212%	0.3184%
2022-01-29	0.0000%	0.2432%	0.2524%	0.4486%	85.0456%	7.6439%	2.4780%	0.9756%	0.7196%	0.4008%	1.0169%	0.4348%	0.3406%
2022-01-30	0.0000%	0.2498%	0.2378%	0.4736%	85.6022%	7.4084%	2.3117%	0.9470%	0.6814%	0.3705%	0.9848%	0.4109%	0.3219%
2022-01-31	0.0000%	0.1921%	0.1645%	0.3336%	86.8529%	7.5929%	1.4485%	0.9938%	0.7046%	0.3647%	0.6753%	0.4006%	0.2765%
2022-02-01	0.0000%	0.1961%	0.1595%	0.4035%	87.0774%	7.3390%	1.4790%	0.9652%	0.6843%	0.3597%	0.6694%	0.3948%	0.2720%
2022-02-02	0.0000%	0.1956%	0.1629%	4.0875%	83.8040%	7.0391%	1.4431%	0.9144%	0.6703%	0.3552%	0.6702%	0.3885%	0.2692%
2022-02-03	0.0000%	0.1961%	0.1534%	10.7877%	77.4577%	6.7343%	1.4876%	0.8727%	0.6411%	0.3440%	0.6779%	0.3804%	0.2672%
2022-02-04	0.0000%	0.2091%	0.2088%	19.5037%	68.9628%	6.4236%	1.5359%	0.8393%	0.6403%	0.3368%	0.6862%	0.3818%	0.2718%
2022-02-05	0.0000%	0.3378%	0.2795%	27.7997%	59.7330%	6.1880%	2.2839%	0.7829%	0.5944%	0.3307%	0.9933%	0.3800%	0.2968%
2022-02-06	0.0000%	0.3490%	0.2758%	30.7760%	56.9533%	6.0346%	2.2841%	0.7652%	0.5892%	0.3248%	0.9688%	0.3856%	0.2937%
2022-02-07	0.0000%	0.2698%	0.2073%	31.2145%	57.4092%	6.0665%	1.6698%	0.8326%	0.6459%	0.3355%	0.6748%	0.3836%	0.2905%
2022-02-08	0.0000%	0.2835%	0.2034%	39.6256%	49.2262%	5.8524%	1.7011%	0.8005%	0.6267%	0.3329%	0.6700%	0.3867%	0.2913%
2022-02-09	0.0000%	0.2854%	0.2040%	51.7434%	37.4438%	5.5967%	1.6149%	0.7902%	0.6179%	0.3346%	0.6811%	0.3886%	0.2994%
2022-02-10	0.0000%	0.3035%	0.2056%	64.1751%	25.4399%	5.1914%	1.6026%	0.7773%	0.6148%	0.3323%	0.6678%	0.3856%	0.3042%
2022-02-11	0.0000%	0.3200%	0.2123%	70.9156%	18.9909%	4.9838%	1.4181%	0.7774%	0.6214%	0.3416%	0.7113%	0.3908%	0.3168%
2022-02-12	0.0001%	0.4216%	0.2739%	75.8758%	12.7559%	4.8394%	2.5110%	0.7159%	0.6017%	0.3329%	0.9718%	0.3929%	0.3072%
2022-02-13	0.0000%	0.4237%	0.2763%	77.6752%	11.3726%	4.6607%	2.3649%	0.6861%	0.5655%	0.3140%	0.9684%	0.3837%	0.3091%
2022-02-14	0.0000%	0.3152%	0.2083%	76.9611%	13.1654%	4.6464%	1.7167%	0.7342%	0.5899%	0.3201%	0.6560%	0.3933%	0.2934%
2022-02-15	0.0000%	0.3124%	0.2021%	79.1282%	11.3529%	4.4636%	1.6466%	0.7071%	0.5653%	0.3201%	0.6274%	0.3832%	0.2912%
2022-02-16	0.0000%	0.3243%	0.2038%	80.6639%	9.9946%	4.2701%	1.6595%	0.7158%	0.5658%	0.3122%	0.6302%	0.3760%	0.2838%
2022-02-17	0.0000%	0.3285%	0.2009%	81.8338%	8.9708%	4.1527%	1.6762%	0.6951%	0.5514%	0.3076%	0.6269%	0.3747%	0.2814%
2022-02-18	0.0008%	0.3497%	0.2078%	82.6826%	8.0582%	4.0522%	1.7689%	0.6878%	0.5474%	0.3209%	0.6655%	0.3684%	0.2897%
2022-02-19	0.0334%	0.3962%	0.3184%	83.4303%	6.2674%	4.0039%	2.4328%	0.6835%	0.5080%	0.3128%	0.9336%	0.3811%	0.2987%
2022-02-20	0.0797%	0.3311%	0.3194%	84.0234%	5.9904%	3.8715%	2.3334%	0.6594%	0.5073%	0.3056%	0.9356%	0.3620%	0.2810%
2022-02-21	0.0587%	0.2598%	0.2468%	84.1764%	6.8024%	3.8159%	1.8127%	0.6649%	0.5265%	0.3067%	0.6597%	0.3832%	0.2862%
2022-02-22	0.0632%	0.2399%	0.2450%	84.9382%	6.4595%	3.6142%	1.7137%	0.6378%	0.5159%	0.3049%	0.6299%	0.3638%	0.2741%
2022-02-23	0.0752%	0.2359%	0.2761%	85.3787%	6.0287%	3.5009%	1.7839%	0.6317%	0.5087%	0.3049%	0.6374%	0.3672%	0.2707%
2022-02-24	0.0705%	0.2362%	0.2634%	85.9954%	5.6871%	3.4246%	1.7009%	0.5988%	0.4996%	0.2919%	0.6033%	0.3600%	0.2683%
2022-02-25	0.0768%	0.2443%	0.2955%	86.3641%	5.2829%	3.3680%	1.7568%	0.5657%	0.4905%	0.2913%	0.6322%	0.3625%	0.2695%
2022-02-26	0.0986%	0.3235%	0.4231%	85.9440%	4.4333%	3.3909%	2.5171%	0.5412%	0.4798%	0.2909%	0.9168%	0.3703%	0.2705%
2022-02-27	0.1076%	0.2852%	0.4442%	86.3178%	4.2554%	3.3355%	2.4455%	0.5217%	0.4657%	0.2732%	0.8975%	0.3688%	0.2820%
2022-02-28	0.0805%	0.2264%	0.3290%	87.0944%	4.7665%	3.2002%	1.7667%	0.5552%	0.4824%	0.2741%	0.6065%	0.3504%	0.2676%
2022-03-01	0.0823%	0.2243%	0.4175%	87.4211%	4.5314%	3.0594%	1.7720%	0.5578%	0.4607%	0.2697%	0.5930%	0.3512%	0.2596%
2022-03-02	0.0813%	0.2251%	3.9680%	84.2254%	4.3094%	3.0111%	1.6974%	0.5485%	0.4639%	0.2678%	0.6025%	0.3420%	0.2575%
2022-03-03	0.0860%	0.2245%	11.9552%	76.5380%	4.1113%	2.9298%	1.6869%	0.5471%	0.4651%	0.2670%	0.5852%	0.3437%	0.2603%
2022-03-04	0.1481%	0.2362%	22.5161%	66.1485%	3.8667%	2.8832%	1.7433%	0.5229%	0.4527%	0.2609%	0.6226%	0.3430%	0.2558%
2022-03-05	0.2483%	0.3164%	33.6288%	54.2056%	3.4509%	3.0747%	2.3631%	0.4963%	0.4430%	0.2635%	0.8942%	0.3452%	0.2699%
2022-03-06	0.2651%	0.3227%	37.2905%	50.9078%	3.3400%	2.9203%	2.2912%	0.4958%	0.4426%	0.2506%	0.8726%	0.3363%	0.2644%
2022-03-07	0.1837%	0.2660%	36.9753%	52.3521%	3.5951%	2.6073%	1.6510%	0.4961%	0.4436%	0.2591%	0.5845%	0.3299%	0.2562%
2022-03-08	0.1921%	0.2728%	46.1578%	43.5044%	3.4375%	2.5065%	1.5931%	0.4913%	0.4273%	0.2568%	0.5841%	0.3277%	0.2486%
2022-03-09	0.1910%	0.2750%	58.6384%	31.1182%	3.3291%	2.5030%	1.5923%	0.4941%	0.4443%	0.2631%	0.5759%	0.3217%	0.2541%
2022-03-10	0.1983%	0.2759%	66.6023%	23.3853%	3.1888%	2.4334%	1.6060%	0.4924%	0.4216%	0.2532%	0.5752%	0.3215%	0.2462%
2022-03-11	0.2169%	0.2953%	71.2820%	18.7575%	3.0712%	2.4137%	1.6315%	0.4822%	0.4248%	0.2533%	0.6013%	0.3233%	0.2471%
2022-03-12	0.3178%	0.3579%	75.0959%	13.7713%	2.8331%	2.6181%	2.3502%	0.5067%	0.4230%	0.2547%	0.8853%	0.3329%	0.2531%
2022-03-13	0.2925%	0.3544%	76.5015%	12.4441%	2.7972%	2.6467%	2.3365%	0.5097%	0.4227%	0.2400%	0.8676%	0.3224%	0.2645%
2022-03-14	0.2183%	0.2980%	76.5209%	13.9213%	2.8796%	2.3086%	1.5790%	0.4721%	0.4184%	0.2446%	0.5742%	0.3196%	0.2454%
2022-03-15	0.2178%	0.2821%	78.3268%	12.3836%	2.7799%	2.2183%	1.5574%	0.4742%	0.4004%	0.2423%	0.5740%	0.3035%	0.2396%
2022-03-16	0.2279%	0.2746%	79.9200%	11.0179%	2.6655%	2.1855%	1.5131%	0.4623%	0.3887%	0.2386%	0.5568%	0.3099%	0.2394%
2022-03-17	0.2330%	0.2813%	81.1027%	9.9678%	2.5655%	2.1601%	1.5065%	0.4504%	0.3991%	0.2343%	0.5593%	0.3033%	0.2366%
2022-03-18	0.2561%	0.2912%	82.1716%	9.0172%	2.4236%	2.0762%	1.5907%	0.4408%	0.3820%	0.2322%	0.5850%	0.3003%	0.2331%
2022-03-19	0.3151%	0.3508%	82.1984%	7.4544%	2.3516%	2.4225%	2.3421%	0.4546%	0.4032%	0.2363%	0.8967%	0.3170%	0.2574%
2022-03-20	0.2713%	0.3462%	82.7299%	7.2246%	2.2897%	2.3687%	2.3127%	0.4359%	0.4056%	0.2296%	0.8447%	0.2944%	0.2466%
2022-03-21	0.1971%	0.2725%	83.3152%	8.0553%	2.3554%	2.0378%	1.6154%	0.4333%	0.3793%	0.2315%	0.5662%	0.3034%	0.2376%
2022-03-22	0.1822%	0.2902%	84.1726%	7.4951%	2.2640%	1.9560%	1.5519%	0.4160%	0.3707%	0.2215%	0.5526%	0.3038%	0.2235%
2022-03-23	0.1787%	0.2905%	84.8110%	7.0357%	2.1387%	1.9110%	1.5677%	0.3992%	0.3727%	0.2213%	0.5465%	0.2992%	0.2279%
2022-03-24	0.1816%	0.2881%	85.3078%	6.6819%	2.0346%	1.8871%	1.5665%	0.4017%	0.3653%	0.2162%	0.5431%	0.2961%	0.2300%
2022-03-25	0.1850%	0.3259%	85.5512%	6.3257%	1.9862%	1.8161%	1.6912%	0.3979%	0.3712%	0.2314%	0.5782%	0.3023%	0.2376%
2022-03-26	0.2513%	0.4347%	84.9980%	5.7174%	1.8887%	1.8396%	2.4636%	0.3976%	0.3775%	0.2233%	0.8562%	0.3074%	0.2447%
2022-03-27	0.2380%	0.4364%	85.5432%	5.6370%	1.7971%	1.7317%	2.3124%	0.3832%	0.3692%	0.2104%	0.8099%	0.2877%	0.2441%
2022-03-28	0.1666%	0.3208%	86.8461%	5.7222%	1.8063%	1.5579%	1.5932%	0.3879%	0.3505%	0.2161%	0.5225%	0.2842%	0.2257%
2022-03-29	0.1513%	0.5652%	87.1876%	5.3979%	1.7323%	1.4451%	1.5669%	0.3681%	0.3506%	0.2009%	0.5336%	0.2811%	0.2194%
2022-03-30	0.1576%	5.5490%	82.6303%	5.1355%	1.6597%	1.3612%	1.5718%	0.3627%	0.3415%	0.2026%	0.5277%	0.2815%	0.2187%
2022-03-31	0.1559%	14.2487%	74.3161%	4.9095%	1.5865%	1.3213%	1.5609%	0.3582%	0.3308%	0.1997%	0.5151%	0.2800%	0.2173%
2022-04-01	0.1813%	25.5917%	63.0197%	4.6924%	1.5348%	1.3091%	1.7270%	0.3518%	0.3366%	0.2027%	0.5498%	0.2824%	0.2208%
2022-04-02	0.2617%	36.0589%	50.8073%	4.7315%	1.5903%	1.4032%	2.7742%	0.3796%	0.3699%	0.2150%	0.8255%	0.3100%	0.2731%
2022-04-03	0.2696%	40.1393%	47.6733%	4.5903%	1.4216%	1.2821%	2.3981%	0.3682%	0.3410%	0.1911%	0.8276%	0.2667%	0.2313%
2022-04-04	0.2050%	40.4830%	49.2044%	4.2831%	1.3593%	1.1840%	1.5060%	0.3320%	0.3082%	0.1899%	0.5062%	0.2527%	0.1862%
2022-04-05	0.2067%	43.9099%	46.1357%	4.0916%	1.3287%	1.1513%	1.4396%	0.3215%	0.3041%	0.1849%	0.4934%	0.2481%	0.1847%
2022-04-06	0.2187%	45.9304%	43.8938%	3.9022%	1.3749%	1.1920%	1.6659%	0.3339%	0.3118%	0.1924%	0.5080%	0.2672%	0.2089%
2022-04-07	0.2248%	55.3760%	34.7892%	3.6035%	1.3432%	1.1667%	1.6971%	0.3292%	0.3116%	0.1860%	0.5093%	0.2567%	0.2067%
2022-04-08	0.2437%	65.3241%	24.9055%	3.4441%	1.3174%	1.1591%	1.7565%	0.3383%	0.3080%	0.1865%	0.5392%	0.2649%	0.2129%
2022-04-09	0.3552%	72.6629%	16.1023%	3.4380%	1.3360%	1.2065%	2.6180%	0.3881%	0.3343%	0.2036%	0.8520%	0.2712%	0.2320%
2022-04-10	0.3588%	75.0152%	14.1712%	3.3374%	1.2959%	1.1573%	2.4802%	0.3769%	0.3273%	0.1896%	0.8174%	0.2547%	0.2182%
2022-04-11	0.2514%	75.1833%	15.7071%	3.0419%	1.2542%	1.1076%	1.6913%	0.3187%	0.3001%	0.1846%	0.5052%	0.2561%	0.1983%
2022-04-12	0.2525%	77.6105%	13.5018%	2.8775%	1.2313%	1.0921%	1.6838%	0.3182%	0.2940%	0.1846%	0.4997%	0.2535%	0.2004%
2022-04-13	0.2515%	79.3135%	11.8381%	2.7657%	1.1999%	1.1073%	1.7596%	0.3188%	0.2942%	0.1894%	0.4959%	0.2597%	0.2064%
2022-04-14	0.2638%	81.6428%	10.2230%	2.6689%	1.0457%	1.0041%	1.5028%	0.2964%	0.2720%	0.1751%	0.4884%	0.2337%	0.1832%
2022-04-15	0.3107%	82.1871%	8.7132%	2.6720%	1.0914%	1.0746%	2.0693%	0.3225%	0.2960%	0.1897%	0.6075%	0.2495%	0.2165%
2022-04-16	0.4049%	82.9440%	6.8725%	2.7691%	1.0718%	1.0948%	2.6616%	0.3438%	0.3227%	0.1963%	0.8405%	0.2559%	0.2221%
2022-04-17	0.4047%	83.4272%	6.5785%	2.7740%	1.0408%	1.0796%	2.5529%	0.3526%	0.3187%	0.1759%	0.8376%	0.2427%	0.2149%
2022-04-18	0.2857%	83.8299%	7.5944%	2.5342%	1.0325%	1.0743%	1.8479%	0.3261%	0.2894%	0.1820%	0.5436%	0.2572%	0.2028%
2022-04-19	0.2766%	84.8091%	7.2881%	2.3503%	0.9702%	0.9922%	1.6394%	0.3148%	0.2756%	0.1719%	0.4804%	0.2454%	0.1860%
2022-04-20	0.2799%	85.4701%	6.7614%	2.2479%	0.9362%	0.9852%	1.6643%	0.3012%	0.2773%	0.1684%	0.4834%	0.2422%	0.1825%
2022-04-21	0.2973%	86.0018%	6.2328%	2.2261%	0.9132%	0.9700%	1.7047%	0.2971%	0.2696%	0.1666%	0.4986%	0.2399%	0.1823%
2022-04-22	0.3213%	86.3868%	5.7889%	2.1593%	0.9105%	0.9627%	1.7757%	0.2977%	0.2819%	0.1722%	0.5237%	0.2371%	0.1822%
2022-04-23	0.4968%	85.8966%	4.7296%	2.4019%	0.8974%	0.9904%	2.5055%	0.3403%	0.3033%	0.1721%	0.8126%	0.2451%	0.2084%
2022-04-24	0.4777%	85.4802%	4.7939%	2.3608%	0.9737%	1.0529%	2.7088%	0.3398%	0.3156%	0.1795%	0.7897%	0.2788%	0.2486%
2022-04-25	0.3257%	87.3284%	5.1208%	2.0780%	0.8546%	0.9471%	1.6892%	0.2974%	0.2703%	0.1654%	0.5006%	0.2404%	0.1822%
2022-04-26	0.4103%	87.7223%	4.8262%	2.0045%	0.8395%	0.9266%	1.6524%	0.2915%	0.2682%	0.1640%	0.4741%	0.2361%	0.1842%
2022-04-27	4.8221%	83.6717%	4.5406%	1.9638%	0.8197%	0.9201%	1.6594%	0.2805%	0.2673%	0.1625%	0.4782%	0.2347%	0.1792%
2022-04-28	10.2662%	78.5895%	4.2556%	1.9180%	0.8044%	0.9025%	1.6505%	0.2883%	0.2675%	0.1639%	0.4822%	0.2347%	0.1769%
2022-04-29	14.2843%	74.6277%	3.9706%	1.9208%	0.8075%	0.9010%	1.8151%	0.2902%	0.2755%	0.1664%	0.5181%	0.2346%	0.1882%
2022-04-30	18.8788%	69.1757%	3.2994%	2.1357%	0.8096%	0.9441%	2.6950%	0.3253%	0.2932%	0.1724%	0.8318%	0.2364%	0.2026%

Chrome, Edge, and Firefox all have similar release cycles with releases every four weeks. Graphing Chrome traffic by version from January through April shows us how quickly older versions of these evergreen browsers fall off. We see peak-to-peak traffic around every four weeks, with a two week period where a single version represents more than 80% of all traffic for that browser.

This shows us that the promise of evergreen browsers is here today. The days of targeting one specific version of one browser are long gone. In fact, trying to do so today would be untenable. The Web Systems Team at GitHub removed the last traces of conditionals based on the user agent header in January 2020, and recorded an internal ADR explicitly disallowing this pattern due to how hard it is to maintain code that relies on user agent header parsing.

With that said, we still need to ensure some compatibility for user agents, which do not fall into the neat box of evergreen browsers. Universal access is important, and 1% of 73 million users is still 730,000 users.

Older browsers

When looking at the remaining 4% of browser traffic, we not only see very old versions of the most popular browsers, but also a diverse array of other branded user agents. Alongside older versions of Chrome (80-89 make up 1%, and 70-79 make up 0.2%), there are also Chromium forks, like QQ Browser (0.085%), Naver Whale (0.065%), and Silk (0.003%). Alongside older versions of Firefox (80-89 make up 0.12%, and 70-79 at 0.09%) there are Firefox forks, like IceWeasel (0.0002%) and SeaMonkey (0.0004%). The data also contains lots of esoteric user agents too, such as those from TVs, e-readers, and even refrigerators. In total, we’ve seen close to 20 million unique user agent strings visiting GitHub in 2022 alone.

Another vector we look at is logged-in vs. logged-out usage. As a whole, around 20% of the visits to GitHub come from browsers with logged-out sessions, but when looking at older browsers, the proportion of logged-out visits is much higher. For example, requests coming from Amazon Silk make up around 0.003% of all visits, but 80% of those visits are with logged-out sessions. Meaning, the number of logged-in visits on Silk is closer to 0.0006%. Users making requests with forked browsers also tend to make requests from evergreen browsers. For example, users making requests with SeaMonkey do so for 37% of their usage, while the other 63% come from Chrome or Firefox user agents.

We consider logged-in vs. logged-out, and main vs. a secondary browser to be important distinctions, because the usage patterns are quite different. Actions that a logged-out user takes (reading issues and pull requests, cloning repositories, and browsing files) are quite different to the actions a logged-in user takes (replying to issues and reviewing pull requests, starring repositories, editing files, and looking at their dashboard). Logged-out activities tend to be more “read only” actions, which means they hit very few paths that require JavaScript to run. Whereas logged-in users tend to perform the kind of rich interactions that require JavaScript.

With JavaScript disabled, you’re still able to log in, comment on issues and pull requests (although our rich markdown toolbar won’t work), browse source code (with syntax highlighting), search for repositories, and even star, watch, or fork them. Popover menus even work, thanks to the clever use of the HTML <details> element.

How we engineer for older browsers

With such a multitude of browsers, with various levels of standards compliance, we cannot expect our engineers to know the intricacies of each. We also don’t have the resources to test on the hundreds of browsers across thousands of operating system and version combinations we see, while 0.0002% of you are using your Tesla to merge pull requests, a Model 3 won’t fit into our testing budget!

Instead, we use a few industry standard practices, like linting and polyfills, to make sure we’re delivering a good baseline experience:

Static code analysis (linting) to catch browser compatibility issues:

We love ESLint. It’s great at catching classes of bugs, as well as enforcing style, for which we have extensive configurations, but it can also be useful for catching cross-browser bugs. We use amilajack/eslint-plugin-compat for guarding against use of features that aren’t well supported, and we’re not prepared to polyfill (for example, ResizeObserver). We also use keithamus/eslint-plugin-escompat for catching use of syntax that browsers do not support, and we don’t polyfill or transpile. These plugins are incredibly useful for catching quirks, for example, older versions of Edge supported destructuring, but in some instances these caused a SyntaxError. By linting for this corner case, we were able to ship native destructuring syntax to all browsers with a lint check to prevent engineers from hitting SyntaxErrors. Shipping native destructuring syntax allowed us to remove multiple kilobytes of transpiled code and helper functions, while linting kept code stable for older versions of Edge.

Polyfills to patch browsers with modern features

Past iterations of our codebase made liberal use of polyfills, such as mdn-polyfills, es6-promise, template-polyfill, and custom-event-polyfill, to name a few. Managing polyfills was burdensome and in some cases hurt performance. We were restricted in certain ways. For example, we postponed adoption of ShadowDOM due to the poor performance of polyfills available at the time.

More recently, our strategy has been to maintain a small list of polyfills for code features that are easy enough to polyfill with low impact. These polyfills are open sourced in our browser-support repository. In this repository, we also maintain a function that checks if a browser has a base set of functionality necessary to run GitHub’s JavaScript. This check expects variables, like Blob, globalThis, and MutationObserver to exist. If a browser doesn’t pass this check, JavaScript still executes, but any uncaught exceptions will not be reported to our error reporting library that we call failbot. By preventing browsers that don’t meet our minimum requirements, we reduce the amount of noise in our error reporting systems, which increases the value of error reporting software dramatically. Here’s some relevant code from failbot.ts:

import {isSupported} from '@github/browser-support'

const extensions = /(chrome|moz|safari)-extension:\/\//
// Does this stack trace contain frames from browser extensions?
function isExtensionError(stack: PlatformStackframe[]): boolean {
  return stack.some(frame => extensions.test(frame.filename) || extensions.test(frame.function))
}

let errorsReported = 0
function reportable() {
  return errorsReported < 10 && isSupported()
}

export async function report(context: PlatformReportBrowserErrorInput) {
  if (!reportable()) return
  if (isExtensionError()) return
  errorsReported++
  // ... 
}

In order to help us quickly determine which browsers meet our minimum requirements, and which browsers require which polyfills, our browser-support repository even has its own publicly-visible compatibility table!

Shipping changes and validating data

When it comes to making a change, like shipping native optional chaining syntax, one tool we reach for is an internal CLI that lets us quickly generate Markdown tables that can be added to pull requests introducing new native syntax or features that require polyfilling. This internal CLI tool uses mdn/browser-compat-data and combines it with the data we have to generate a Can I Use-style feature table, but tailored to our usage data and the requested feature. For example:

browser-support-cli $ ./browsers.js optional chaining

#### [javascript operators optional_chaining](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Operators/Optional_chaining)
| Browser                 | Supported Since | Latest Version | % Supported | % Unsupported |
| :---------------------- | --------------: | -------------: | ----------: | ------------: |
| chrome                  |              80 |            101 |      73.482 |         0.090 |
| edge                    |              80 |            100 |       6.691 |         0.001 |
| firefox                 |              74 |            100 |      12.655 |         0.014 |
| firefox_android         |              79 |            100 |       0.127 |         0.001 |
| ie                      |   Not Supported |             11 |       0.000 |         0.078 |
| opera                   |              67 |             86 |       1.267 |         0.000 |
| safari                  |            13.1 |           15.4 |       4.630 |         0.013 |
| safari_ios              |            13.4 |           15.4 |       0.505 |         0.006 |
| samsunginternet_android |            13.0 |           16.0 |       0.020 |         0.000 |
| webview_android         |              80 |            101 |       0.001 |         0.008 |
| **Total:**              |                 |                |  **99.378** |     **0.211** |

We can then take this table and paste it into a pull request description to help provide data at the fingertips of whoever is reviewing the pull request, to ensure that we’re making decisions that are inline with our principles.

This CLI tool has a few more features. It actually generated all the tables in this post, which we could then easily generate graphs with. For quick glances at feature tables, it also allows for exporting of our analytics table into a JSON format that we can import into Can I Use.

browser-support-cli $ ./browsers.js
    Usage:
      node browsers.js <query>
    Examples:
      node browsers.js --stats [--csv]    # Show usage stats by browser+version
      node browsers.js --last-ten [--csv] # Show usage stats of the last 10 major versions, by vendor
      node browsers.js --cadence [--csv]  # Show release cadence stats
      node browsers.js --caniuse          # Output a `simple.json` for import into caniuse.com
      node browsers.js --html <query>     # Output html for github.github.io/browser-support

Wrap-up

This is how GitHub thinks about our users and the browsers they use. We back up our principles with tooling and data to make sure we’re delivering a fast and reliable service to as many users as possible.

Concepts like progressive enhancement allow us to deliver the best experience possible to the majority of customers, while delivering a useful experience to those using older browsers.

Written by

Keith Cirkel

@keithamus