It seems negative lookbehind expressions (which should be valid in both Ruby and JS flavors of regex, the latter as of ECMAScript 2018) don’t work in Watched Words. Here’s an example: (?<!new\s)\bcar\b should match instances of car that are not preceded by new. E.g. it should match car in this sentence: He drives a car But not in this sentence: He drives a new car However, it returns the following error when adding under Watched Words: [Regex error] Is this not supported on purpose or is it a bug? Or does it need to be written in a different way?

Welcome, Thomas :slight_smile: I don’t encounter this issue: [image]

Does it also work for you for automatic linking?

It seems, yes. [Screenshot_20230718_193943_Chrome] [Screenshot_20230718_194053_Chrome]

Strange that it’s not working for me then. I’m currently on 3.1.0.beta4, will upgrade to the latest and try again…

Interestingly, it seems to be browser-dependent. I get the error in Safari, but not in Chrome. When adding it in Chrome and viewing the list in Safari the error shows up there. But I guess I can just ignore it for now.

I tried it on Chrome (Windows) and Safari 16.5.2 and I still couldn’t reproduce your issue. :thinking:

Turns out it’s only supported from Safari 16.4, and I had 16.3. Still causing other issues for me, though (like can’t save my user preferences): [image] What could be causing 500 errors when saving user preferences? Support So I guess it might actually have been this error: [CleanShot 2023-08-03 at 12.17.58@2x] I figured that one was just showing up due to this issue: However, it turns out it’s all related. Here are the full logs: Info: RegexpError (invalid pattern in look-behind: /((?<!estonia.*\s)\be-residence\b(?!.*estonia))/i) app/services/word_watcher.rb:264:in `initialize' app/services/word_watcher.rb:264:in `new' app/services/word_watcher.rb:264:in `block in replace' app/services/word_watcher.rb:262…

Negative lookbehind not working in watched words regex

Product Support

Canapin (Coin-coin le Canapin) July 18, 2023, 2:13pm 2

Welcome, Thomas

I don’t encounter this issue:

Topic		Replies	Views
Watched word regular expression crash Bug watched-words	6	1012	November 29, 2023
Test Watched Words is Broken Bug watched-words	2	633	June 9, 2023
Invalid regular expressions in 'Watched Words' makes no watched word work Bug watched-words	2	722	May 31, 2021
Watched word regular expression crash (2025) Bug regex , watched-words	6	391	October 6, 2025
Rules for Number Matching in Watched Words Bug watched-words	3	226	February 21, 2026

Negative lookbehind not working in watched words regex

Related topics