High Resolution Time API

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	W3C Recommendation

IE	Edge	Firefox	Chrome	Safari	Opera
			73
		65	72
		64	71	TP
11	18	63	70	12	56
10	17	62	69	11.1	55
9	16	61	68	11	54
8	15	60	67	10.1	53
Show all
7	14	59	66	10	52
6	13	58	65	9.1	51
5.5	12	57	64	9	50
		56	63	8	49
		55	62	7.1	48
		54	61	7	47
		53	60	6.1	46
		52	59	6	45
		51	58	5.1	44
		50	57	5	43
		49	56	4	42
		48	55	3.2	41
		47	54	3.1	40
		46	53		39
		45	52		38
		44	51		37
		43	50		36
		42	49		35
		41	48		34
		40	47		33
		39	46		32
		38	45		31
		37	44		30
		36	43		29
		35	42		28
		34	41		27
		33	40		26
		32	39		25
		31	38		24
		30	37		23
		29	36		22
		28	35		21
		27	34		20
		26	33		19
		25	32		18
		24	31		17
		23	30		16
		22	29		15
		21	28		12.1
		20	27		12
		19	26		11.6
		18	25		11.5
		17	24		11.1
		16	23 (*)		11
		15	22 (*)		10.6
		14	21 (*)		10.5
		13	20 (*)		10.0-10.1
		12	19		9.5-9.6
		11	18		9
		10	17
		9	16
		8	15
		7	14
		6	13
		5	12
		4	11
		3.6	10
		3.5	9
		3	8
		2	7
			6
			5
			4

iOS Safari	Opera Mini	Android Browser	Blackberry Browser	Opera Mobile	Android Chrome	Android Firefox	IE Mobile	Android UC Browser	Samsung Internet	QQ Browser	Baidu Browser
12	all	67	10	46	70	63	11	11.8	7.2	1.2	7.12
11.3-11.4		4.4.3-4.4.4	7	12.1			10		6.2
11.0-11.2		4.4		12					5
10.3		4.2-4.3		11.5					4
Show all
10.0-10.2		4.1		11.1
9.3		4		11
9.0-9.2		3		10
8.1-8.4		2.3
8		2.2
7.0-7.1		2.1
6.0-6.1
5.0-5.1
4.2-4.3
4.0-4.1
3.2

Notes

The timestamp is not actually high-resolution. To mitigate security threats such as Spectre, browsers currently round the result to varying degrees.

1. In Firefox, the "privacy.reduceTimerPrecision" preference is enabled by default and defaults to 20us in Firefox 59; in 60 it will be 2ms.

2. In Firefox, the "privacy.resistFingerprinting" preference changes the precision to 100ms or the value of "privacy.resistFingerprinting.reduceTimerPrecision.microseconds", whichever is larger.

^* Partial support with prefix.

Bugs

• 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).

• 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

Resources

• MDN Web Docs - Performance.now
• HTML5Rocks article
• SitePoint article
• Demo