The hidden meaning of 537.36 in the Chromium User-Agent string

28 May 2021

If you’re like me, first of all, very sorry to hear that, but you are probably spending your Friday morning wondering what the meaning of 537.36 is in the Chromium User-Agent string. It appears in two places: AppleWebKit/537.36 and Safari/537.36.

As any serious researcher does, the first place I went to for answers was, to check out the “Angel Number Spiritual Meaning”.

(I enjoy a good data-collection-scheme-disguised-as-fortune-telling site as much as anyone else, don’t judge me.)

engraving an angel with 2 horns, blowing the numbers 537 and 36

537 means:

“Positive changes in the material aspect will be an extra confirmation that you have made the right choice of a life partner”

And 36 means:

“[Y]es, you are doing everything right, but you are not doing everything that you could do”.

Angels probably use PHP, so let’s assume “.” is the string concatenation operator. Mashing those together, a meaning emerges: “537.36” represents the last shipping version of WebKit before the Blink fork.

Back in 2013 (right after the fork announcement), Ojan Vafai wrote,

“In the short-term we have no plans of changing the UA string. The only thing that will change is the Chrome version number.”

Darin Fisher (former engineering lead for the Chrome Web Platform Team) said the same in the recorded Q&A video (linked from the Developer FAQ).

Assuming Wikipedia is as trustworthy as that “why did I give the Angel Numerology site my email, birthdate, relationship status, and name, and why am I getting so many ads on other sites about healing crystals and clearance specials on hydroxychloroquine??” site, Chrome 27.0.1453 was the last version of Chrome shipping WebKit, which was at 537.36, and Chrome 28.0.1500 was the first version of stable channel release shipping the Blink engine.

So that’s why those numbers are in the User-Agent string. For obvious compatibility reasons, you can’t just remove strings like AppleWebKit/537.36 and Safari/537.36. And that’s why we’ll keep them there, likely frozen forever.