HTMX Universal Standards
Core Philosophy (HATEOAS)
- HTML over JSON: The server MUST respond with HTML fragments (partials), not JSON.
- Side Effects via HTML: Do not use client-side logic to update the DOM. Let the server response dictate changes via
hx-swap.
Security & CSRF (Critical)
- CSRF Protection: HTMX requests are non-idempotent (POST/PUT/DELETE) and require CSRF protection just like standard forms.
- Header Method: Configure the global hx-headers to include the token: <body hx-headers='{"X-CSRF-Token": "{{csrfToken}}"}'>. - Form Method: If headers aren't viable, ensure every <form> includes the hidden CSRF input.
- XSS Prevention: Since we are injecting HTML, ensure all user content rendered on the server is strictly escaped before reaching the client.
Architectural Rules
- The "Partial" Rule: Identify strictly which part of the UI needs updating. Create a server route that renders *only* that component.
- Idempotency: GET requests should never change state. Use POST/PUT/PATCH/DELETE for actions.
- Progressive Enhancement: Design the feature to work with standard HTML forms/links first where possible.
UX & Feedback Patterns
- Request Indicators: ALWAYS use
hx-indicator.
- Pattern: <button hx-post="..." hx-indicator="#loading-spinner">Save</button>
- Active States: Use the
htmx-addedclass orhx-valsto manage active states via server rendering.
Error Handling Protocol
The backend must communicate status via HTTP Codes:
- 200 OK: Swap content normally.
- 204 No Content: Do nothing.
- 422 Unprocessable Entity: Validation error. Swap the form with the HTML containing error messages.
- HX-Retarget: Use this header if an error requires updating a global element (like a top-level alert) instead of the local target.