Flag in a comment
Inspect the page source and find information hidden in an HTML comment.
Solve challenge → No login requiredDEVTOOLS IN PRACTICE
Look beneath the surface.
Find hidden information and explore how HTTP requests work. Practise on prepared pages using your browser’s developer tools.
- HTML and page source
- HTTP headers
- Cookies and browser data
No login · No installation · Free
Three challenges to get you started
From finding information to changing data. Start with the basics or pick the next level.
The role cookie
Explore what happens when an application trusts a role stored in a cookie.
Solve challenge → No login requiredForged role token (Base64)
Inspect a Base64 token and explore what happens when its authenticity is never verified.
Solve challenge → No login requiredReady for more?
Explore 50 DevTools challenges — from inspecting pages to modifying HTTP requests.
See all DevTools challenges →The full catalogue requires a free account.
How should you approach these challenges?
DevTools exercises develop skills used in web application testing and frontend debugging. You learn to connect what appears on the page with the data being exchanged, for example distinguishing a display issue from an unexpected server response.
These challenges explore page inspection and communication between the browser and server: you find a hidden flag or change data to meet a task’s condition. Use “Open target” to open the prepared page, then launch DevTools (F12). Start by observing: inspect the HTML, examine HTTP requests and responses in the Network panel, and check cookies in browser storage. Form a hypothesis, change one element, and compare the result after repeating the request. Changing the page’s appearance does not necessarily change server data — pay attention to what the browser actually sends and receives. Enter the flag you find on the challenge page.
Put it into practice: Flag in a comment →
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