Learning
Hands-on Labs & Sandboxes
Places to run something now, without installing anything or risking a bill.
Where to start
These are environments rather than courses — the answer to "I want to try this but not on my machine". Anything needing a card is marked free-tier. Watch the session limits: most delete your work when the tab closes, so commit to a repository as you go.
Terminals and clusters3
- KillercodaCoreFree
Interactive terminal scenarios in the browser — Kubernetes, Linux, Docker. The successor to Katacoda after O’Reilly retired it.
- Play with DockerCoreFree
A throwaway Docker host in a browser tab, four hours at a time. Ideal for trying compose files.
- InstruqtCoreFree tier
Vendor-built hands-on tracks, many of them free, on real infrastructure rather than a simulation.
Code and notebooks6
- Google ColabStart hereFree tier
A hosted Python notebook with a free GPU allocation. Where most people run their first model.
- StackBlitzStart hereFree tier
Runs Node in the browser itself, so a full dev server starts in about a second with nothing installed.
- CodeSandboxStart hereFree tier
Full project sandboxes with real containers. Better than StackBlitz when you need the actual filesystem.
- ReplitStart hereFree tier
Multi-language online IDE with hosting. Good for teaching, since a link is a running program.
- GitHub CodespacesCoreFree tier
A full VS Code environment attached to a repository, with a monthly free allowance on personal accounts.
- Jupyter: Try itStart hereFree
Jupyter running in the browser with nothing installed, including the newer JupyterLite build.
Single-purpose scratchpads4
- Regex101Start hereFree
Explains a regular expression token by token as you type. The debugger the language never gave you.
- SQL FiddleStart hereFree
Build a schema and run queries against several database engines side by side. Useful for settling arguments.
- Compiler ExplorerAdvancedFree
See the assembly your code compiles to, across compilers and flags. The fastest way to understand what the optimiser does.
- CyberChefCoreFree
Encoding, decoding, hashing and forensics as drag-and-drop operations. Runs entirely in the browser.
About this list
13 resources, checked automatically every week so dead links do not sit here unnoticed. Nothing on this page is sponsored and none of these links pay us — which is the only reason a recommendation on it is worth anything. Every link goes to the original source, and we take nothing with you when you leave.