CSRF Protection in Form Actions
Understand how SvelteKit prevents cross-site request forgery in form actions.
CSRF Protection in Form Actions is a free Sveltejs Academy lesson on CoddyKit — lesson 1 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the Sveltejs Academy learning path, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.
What CSRF Is
Cross-Site Request Forgery tricks an authenticated user's browser into submitting a forged request to your site.
SvelteKit Default
SvelteKit form actions block requests from cross-origin sources by default, mitigating CSRF.
How It Works
SvelteKit checks the Origin header against the host for state-changing methods.
Same-Site Cookies
Set sameSite: "lax" on cookies as a defense-in-depth measure.
Disable Carefully
You can disable CSRF protection via csrf: { checkOrigin: false } in svelte.config.js. Almost never recommended.
External Form Posts
If you must accept cross-origin posts, use API tokens instead.
Test CSRF
Try submitting to your form from an unrelated origin (e.g. JSFiddle) — SvelteKit should reject it.
GET Methods
GET requests are not CSRF-protected by default; never use GET for state changes.
Combined Defenses
Combine SameSite cookies, Origin checks, and authentication tokens for layered security.
Common Mistakes
Storing JWTs in localStorage and reading them in fetch defeats SameSite protection.
Audit Trail
Log suspicious cross-origin attempts to catch attacks early.
Quick Check
What does SvelteKit check by default for CSRF?
Recap
SvelteKit blocks cross-origin POSTs by default. Combine with SameSite cookies and never disable lightly.
Frequently asked questions
Is the “CSRF Protection in Form Actions” lesson free?
Yes — the full text of “CSRF Protection in Form Actions” is free to read here on the web, and the Sveltejs Academy course includes 4 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the Sveltejs Academy course, upgrade to CoddyKit PRO.
What will I learn in “CSRF Protection in Form Actions”?
Understand how SvelteKit prevents cross-site request forgery in form actions. You practise Sveltejs Academy with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.
Do I need any experience to start Sveltejs Academy?
No prior experience is required. Sveltejs Academy on CoddyKit is structured for beginners through advanced learners; this is — lesson 1 of 4, so you can start here or from the beginning and move at your own pace.
How long does the “CSRF Protection in Form Actions” lesson take?
Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.
Can I write and run code in this Sveltejs Academy lesson?
Yes. Every Sveltejs Academy lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.
All lessons in this course
- CSRF Protection in Form Actions
- XSS Prevention in {#html}
- Environment Variables: $env/static and $env/dynamic
- Rate Limiting with Hooks