W3Challs
Find flags in web, crypto, pwn, reversing and forensics challenges
W3Challs is a community site of hacking challenges. You exploit a weakness in each challenge to find a flag, which is wrapped in a W3C{...} tag, and submit it for points.
Free · Browser · Intermediate
About W3Challs
Challenges come in six categories: crypto, forensics, misc, pwning, reversing and web. That mix suits people who want practice across many areas, from web flaws to binary exploitation.
The site runs in the browser, and you can ask for help in the forums, on IRC or through private messages. It has login and register options for tracking your progress.
On Breakpoint since 23 Oct 2026.