What CSP does
A content security policy tells the browser which sources of scripts, styles, and other content are trusted. It is a strong defense against cross site scripting.
- It blocks inline scripts unless explicitly allowed.
- It restricts where scripts and frames may load from.
- Violations can be reported so you see what would break.
Rolling out safely
Deploy in report only mode first, collect reports, then enforce once the policy is clean.
Techniques at scale
- Use a nonce or hash per response so inline scripts can be allowed precisely.
- Avoid broad allow lists that weaken the policy back toward nothing.
- Centralize policy generation so every team inherits a safe baseline.
Operational notes
- Watch the violation report stream for new third party scripts.
- Version the policy and roll changes gradually behind report only.
- Beware that one weak directive can undermine the whole policy.
Key idea
CSP at scale means rolling out in report only mode, using nonces instead of broad allow lists, and centralizing the baseline so the policy stays strong everywhere.