{ "title":"High Resolution Time API", "description":"Method to provide the current time in sub-millisecond resolution and such that it is not subject to system clock skew or adjustments. Called using `performance.now()`", "spec":"https://www.w3.org/TR/hr-time/", "status":"rec", "links":[ { "url":"https://developer.mozilla.org/en-US/docs/Web/API/Performance.now()", "title":"MDN Web Docs - Performance.now" }, { "url":"https://developer.chrome.com/blog/when-milliseconds-are-not-enough-performance-now/", "title":"HTML5Rocks article" }, { "url":"https://www.sitepoint.com/discovering-the-high-resolution-time-api/", "title":"SitePoint article" }, { "url":"https://audero.it/demo/high-resolution-time-api-demo.html", "title":"Demo" } ], "bugs":[ { "description":"Older versions of Chrome and Opera on Windows have only millisecond precision. The fractional part is always near the very start or the very end of a millisecond. ([issue #158234](https://code.google.com/p/chromium/issues/detail?id=158234))." }, { "description":"The Spy in the Sandbox vulnerability is a class of JavaScript-based exploits that leverage the High Resolution Time API to detect CPU cache hit/miss on chosen plaintext data placed into cache by an attacker. [Full security research paper is here](http://arxiv.org/abs/1502.07373)" } ], "categories":[ "JS API" ], "stats":{ "ie":{ "5.5":"n", "6":"n", "7":"n", "8":"n", "9":"n", "10":"y", "11":"y" }, "edge":{ "12":"y", "13":"y", "14":"y", "15":"y", "16":"y", "17":"y", "18":"y", "79":"y", "80":"y", "81":"y", "83":"y", "84":"y", "85":"y", "86":"y", "87":"y", "88":"y", "89":"y", "90":"y", "91":"y", "92":"y", "93":"y", "94":"y", "95":"y", "96":"y", "97":"y", "98":"y", "99":"y", "100":"y", "101":"y", "102":"y", "103":"y", "104":"y", "105":"y", "106":"y", "107":"y", "108":"y", "109":"y", "110":"y", "111":"y", "112":"y", "113":"y", "114":"y", "115":"y", "116":"y", "117":"y", "118":"y", "119":"y", "120":"y", "121":"y", "122":"y", "123":"y", "124":"y", "125":"y", "126":"y", "127":"y", "128":"y", "129":"y", "130":"y", "131":"y", "132":"y", "133":"y", "134":"y", "135":"y", "136":"y", "137":"y", "138":"y", "139":"y", "140":"y", "141":"y", "142":"y", "143":"y", "144":"y", "145":"y" }, "firefox":{ "2":"n", 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"29":"y" }, "and_qq":{ "14.9":"y" }, "baidu":{ "13.52":"y" }, "kaios":{ "2.5":"y", "3.0-3.1":"y" } }, "notes":"The timestamp is not actually high-resolution. To mitigate security threats such as Spectre, browsers currently round the result to varying degrees.", "notes_by_num":{ "1":"In Firefox 55-57, the `privacy.resistFingerprinting` preference can be enabled to change the precision to 100ms.", "2":"In Firefox, the `privacy.resistFingerprinting` preference can be enabled to change the precision to 100ms or the value of `privacy.resistFingerprinting.reduceTimerPrecision.microseconds`, whichever is larger.", "3":"In Firefox 58-59, the `privacy.reduceTimerPrecision` preference is enabled by default and defaults to 20us.", "4":"In Firefox, the `privacy.reduceTimerPrecision` preference is enabled by default and defaults to 2ms." }, "usage_perc_y":97.51, "usage_perc_a":0, "ucprefix":false, "parent":"", "keywords":"performance,now,testing", "chrome_id":"5349124069130240", "shown":true }