From my experience, most of the big projects in the JavaScript ecosystem are very welcoming to first time contributors. To make your first "valuable" contribution I'd suggest you pick a project that you are using yourself. Read documentation and turn on notifications for issues on GitHub and very quickly you will realize that a lot of people make small yet valuable contributions (documentation, small refactoring etc) without knowing all the details of the source code. At least that has been my experience so far. Last year when my first "feature code" pull request was merged, I wrote a post about the experience: maurobringolf.ch/2017/07/open-source-9-steps-to-m… Although thats more geared towards contributing long-term rather than just one small first contribution, but maybe it helps anyway.

github.com/kriadmin/30-seconds-of-python-code This my repository which you can contribute to. I am also a newbie to python so you will understand all of the code(most of it is 30-second google search). :)

I’m working on a project to help beginners get started on contributing open source projects. github.com/Roshanjossey/first-contributions It’d be awesome if you could check it out and gimme feedback

A resource you may find valuable: firsttimersonly.com

And github filtered by the first-timers-only label: github.com/search

I do contribute to the Matrix.org ecosystem and a bunch of Flask extensions. I also have some minor commits and documentation fixes in various GNOME apps and libraries. But I have much better suggestions for you at the end.

In Matrix, I write the GLib SDK. It is written in C (I prototyped in Vala, and I’m in the middle of porting it back to C). I also contribute a bit to the general discussion around the protocol.

For Flask it’s a bit more diverse. I wrote some extensions myself, as a lot (most) of packages are provided by different members of the community. Most of them are very friendly, but unless you contribute directly to Flask and Werkzeug, you won’t find a central stearing force.

For GNOME I’m primarily an enthusiastic user. My main contributions are bug reports (I can’t emphasize enough how important this is for FL/OSS projects!), but I have some translations, documentation patches, and minor bugfixes in there.

I also contribute to various Emacs packages, but most of them are only significant to a few users.

All that said I suggest a different approach. Create a list of your most used open source projects. List all apps and libraries you use on a daily basis.

Now comes the hard part. Hunt for bugs and annoyances. Find potential missing features. Open the projects’s issue tracker, and look around if anyone reported these. This will be a lot of reading, but you will have two important takeaways from it: a list of core(ish) contributors and the way things go. Even though most projects have some contributor guidelines, it’s much better to look around and see how it goes.

Now that you are familiar with the know-how, go and do it. It’s generally better to start small. Fix a typo. Fix a minor bug. Bring up your feature idea. Then, when they got used to your presence, you can go bigger.

Good luck!

I have never been a dedicated contributer to open source, but I do give my feedback, and eventually pull requests, when I find something I feel need:

gitlab.com/gitlab-org/gitlab-ce/issues/39335