performance.now() may return non-integers in some browsers

[JackDunnCodes]

MDN URL

https://developer.mozilla.org/en-US/docs/Web/API/Performance/now

What specific section or headline is this issue about?

No response

What information was incorrect, unhelpful, or incomplete?

Firefox produces an integer when calling this function. However, Chromium can (and often does) produce a decimal. This information is seemingly missing from this page. This caused strange bugs for me that were difficult to debug until I realised I was using Firefox, and the user was using Chrome.

What did you expect to see?

A section somewhere (not sure where, otherwise I'd write a PR myself) to detail the difference in behaviour between browser. I do not feel the tiny footnote in the compatibility table is enough.

Do you have any supporting links, references, or citations?

No response

Do you have anything more you want to share?

Happy to assist with further detail should you need it, or to write a PR myself with your guidance, don't hesitate to reply.

MDN metadata

Page report details

• Folder: en-us/web/api/performance/now
• MDN URL: https://developer.mozilla.org/en-US/docs/Web/API/Performance/now
• GitHub URL: https://github.com/mdn/content/blob/main/files/en-us/web/api/performance/now/index.md
• Last commit: 566d11b
• Document last modified: 2025-08-25T23:12:47.000Z

[Josh-Cena]

Out of curiosity what code did you write that would break with non-integer timestamps?

[JackDunnCodes]

Out of curiosity what code did you write that would break with non-integer timestamps?

I was using this to generate (part of) a unique ID, that was then put into jQuery as a selector. At that point, it started interpreting the decimal part as a class. My use case is probably niche but I can imagine it being more a problem if e.g. it's sent to a server that expects ints in an Ajax call