I think you’ll find all kinds of ‘libraries’ for doing that, especially in small embedded devices with a web front-end.

I also fear there’s software that correctly extracts all the digits of the version in the user agent, but then compares it as a string with a given version. That would get you

   “100” < “99”

Here's a real example of that bug:

Slack's message buttons (such as "Add reaction" or "Reply in thread") stopped working for Firefox versions >= 100 and <= 519. They mysteriously started working again for versions >= 520. The version string "100" compared as smaller than "52" in Slack's code, which activated some kind of webcompat workaround intended for Firefox versions < 52 that breaks on more recent Firefox versions.

https://github.com/webcompat/web-bugs/issues/67866

This is the same field that thought they could save a year as two digits and didn't think their software would still be in use 30 years later.

It's not crap, it's just short sighted.

True, but user-agent was 1996(?). By then, we weren't talking about limited mainframe storage devices.

It just baffles that someone can look at a monotonically increasing number, defined and incremented by a third party, and say "That will never be 3 digits."

I'd wager it's mostly fixed string indexes, regular expressions ("\d{2}"), and things like that. Maybe also some people with a "varchar(2)" column in the database.

A lot of software is written by junior programmers, not infrequently in a hurry. It's an easy mistake to make and if you've been bitten by it once you'll remember it, but many people have never been bitten by it.

Well, keep in mind that major version numbers used to change slowly. In the first ten years Firefox existed, it went from version 0.1 to version 5.0. At that pace, it would have taken two hundred years to hit a three-digit major version. In my opinion, browser vendors brought this upon themselves by changing what "major version" meant.

To be fair, in 1970 those 2 digits were very expensive. It was a calculated tradeoff at worst.

> To be fair, in 1970 those 2 digits were very expensive.

More than just "very expensive". Often, you were limited to exactly 80 columns for each record. If you had for instance three dates on one record, using 2 digits instead of 4 digits saved 6 columns, which is over 7% of the available space.

I wouldn't be so confident that the code is coming from a library. We take code distribution for granted these days, but some fraction of the web today was built when the only way to get anything done was hand-rolled perl scripts.

I admit it's crap, but I once added a temporary fix to a system of mine that blocked clients with a user agent matching "Chrome 54" (at the string level) due to a bot (I know it's not ideal, but it worked in the moment, and genuine users were no longer using such an old version). I doubt Chrome 540 would turn up any time soon, but I can picture other folks having done similar things with "Chrome 12", say, and wondering why things fail with Chrome 120(!)

That's the speculated reason why Microsoft had to skip Windows 9: because in the late 90s, software were checking for «starts with "Windows 9"» to identify Windows 95 and 98... and some of those checks still exist and would had identified Windows 9 as Windows 95/98.

"New dependencies need to be approved by xyz"

"Ok"

if(userAgent.includes("Chrome") && userAgent[whatever] >= 4)

very optimistic point of view.