Hello! This is a collection of Free/Freemium online resources for CS self teaching/revision, focusing more on Web Development, coding, and Software development resources.If you have any corrections (or suggestions for resources to add), please contact me via email.

>>Useful catchall websites

Teach yourself CS- While I can't in good faith call this a "free resource" as it points to a mix of free, paid and pricy courses and textbooks, it is a good overview of the fundamentals needed for complete beginners.
Isaac Computer Science- A website created by the University of Cambridge and the Raspberry Pi Foundation, it has pretty much everything you could need up to A-Level.
PMT- Physics and Maths tutor have a collection of on-spec computer science notes, flashcards, questions and exam papers.
AQA website- A good list of websites and further reading for both learning and teaching computer science, and a few programming languages.
Craig'N'Dave- A set of videos that cover the CS A-level spec ad nauseum. Note; the mic quality overall is rather bad and volume spikes can trigger sensory overwhelm.

>>Documentation-like resources

Mozilla Docs- An expansive documentation archive for web development. It also includes tutorials, learning resources for anything web/network related, and use cases.
Devdocs.io- Devdocs contains refences for every inbuilt feature for a wide range of popular programming languages (and libraries).
OverAPI- OverAPI is a collection of cheetsheets that show every feature of many languages in a poster-like format, then allows you to click any specific function to be linked to where it can be found in the official documentation.
Algorithm Visualiser- Less documentation, moreso a collection of algorithms, the code for the basic use case, and how they are visualised.
W3Schools- Similar to Mozilla Docs, but more accessible towards wider age ranges. It does cover more languages, but to slightly less depth.

>>Competitive coding

Leetcode- The most well known website for this section; it contains an expansive set of questions and is built deliberately to train for coding interviews- though does routinely host competitions.
Hackerrank- Similar to leetcode, but is particularly known for its "hackathon" it hosts.
Codeforces- Codeforces is explicitly competitive coding only. It has a selection of challenges, and has competitions hosted frequently.
OverAPI- OverAPI is a collection of cheetsheets that show every feature of many languages in a poster-like format, then allows you to click any specific function to be linked to where it can be found in the official documentation.
Coding game- Designed to make competitive programming more interactive and fun.
Topcoder- It has a selection of challenges, but also doubles as a place for recruiters to scout employees.
Codewars- Similar to leetcode, but a lot more community driven, and is more targeted at improving general capabilities than preparing for interviews.
Frontend Mentor- Similar to topcoder, but specifically for frontend development.

>>Learning Resources

Codex.io- catered towards all ages who are complete beginners to coding. It covers python.
Neetcode.io- Neetcode was created to help people learn programming, due to Leetcode having a steep learning curve not accessible to beginners.
Stackup- Similar to topcoder, it provides learning resources and problems which allow you to learn, while providing you with cash reward puzzles.
Traversy Media- A youtube channel that gives comprehensive code walkthroughs and tutorials, primarily in fullstack web development.
Fullstack Open- An online course in web development, especially using frameworks. Its recommended to already have a bit of knowledge to use this course, however.
The Odin Project- An incredibly helpful online course which is recognised by many. However, to use this its highly reccomended to be using OSX or Linux. Windows has had many issues with some of the steps, and in the case you are a windows user it's recommended to use a virtual machine. Other than that, it's the ideal beginner to advanced course, and is incredibly comprehensive.
RapidAPI- Rapid API contains many courses to show you how to build your own API's from the ground up.
CSS Diner- A fun little website to learn all the CSS selectors available.
Freshman.tech- If you prefer being a part of a community, this is ideal. It's essentially a blogging social media geared specifically towards computer science and software dev.
JS tutorial- A complete tutorial to javascript!
Git tutorial, setup and use.- What it says. Git is industry standard so it's important to be proficient.
FreeCodeCamp- A well known website that teaches you how to utilise common programming languages, and has a variety of tutorials for specific use cases.
Tutorials Point- A freemium website that contains free and paid courses, some with certification.
Python Tutor- A website for running code line by line, and showing the result like a trace table.
Hackinscience- If you want to practice all the capabilities of python by solving exercises, I would recommend this. It's a similar format to many compatitive coding platforms, but designed in a more "curriculum" way.

>>Miscellaneous

MonkeyType- Never a bad thing to improve your touch typing, considering how much you'll need to type.
GoodBrief.io- For generating GUI/UIX prompts.
Figma- If you plan on working with frontend a lot, specifically CSS, Figma is invaluable for making prototypes. Though, its best to be wary at the moment as Adobe has recently aquired a business deal with them, so it may move from a freemium service to a subscription in the future.
Developer Roadmaps- Includes many roadmaps, and a few contain learning resources. However, many of these are incomplete to the point I would be unable to put it in the above category. (However the ones they do have are high quality.)
Netifly- Netifly is a freemium website hoster, that serves its purpose well enough.
Carbon- If you ever plan on displaying source code snippets, this presents them nicely.
Oh @$!&, Git!- For git, going over the common disastrous git mistakes and how to undo it.
StackOverflow- An incredibly useful website where you can get solutions and pointers on questions regarding code and errors, however this is not a beginner friendly website, and I reccomend you take note of their "How to ask a question" page, as they crack down hard on new users asking repeat questions, or "low quality" questions, which can lead to suspended accounts.
RegExr- A website that allows you to build and test use cases of Regular Expressions
DevTo- A blogging social media for developers. It contains a wealth of tutorials and discussions.