What is Content-Security-Policy (CSP) Builder?
Content-Security-Policy (CSP) Builder is a browser-based utility for security-focused
developer work. It helps you transform, inspect, generate, or evaluate the relevant input without installing
a separate desktop tool.
How to use this tool
Enter or paste the required input, select the available options, then review the
generated result before copying or applying it in your project. Check the output in its real target
environment when accuracy matters.
Applying Content-Security-Policy (CSP) Builder to a real task
Build a Content Security Policy from the resources the application actually loads. Inventory scripts, styles, images, fonts, connections, frames, and workers, then allow only the origins and mechanisms each directive requires. Avoid broad wildcards and unsafe-inline or unsafe-eval unless a documented compatibility need has been assessed. A policy that is too strict can break legitimate features; one that is too broad provides little protection. Test a proposed policy in report-only mode where the deployment supports it, review violations, and then enforce a carefully scoped header.
Prepare the input and options
Start with a representative but bounded sample. Large or mixed inputs can make it harder to tell whether a result is caused by the data, the selected options, or an unsupported edge case. Pay attention to these page fields: default-src, script-src, style-src. Confirm which fields are inputs, options, or output areas before processing. Keep notes on any assumption that changes how the result should be interpreted.
Run and inspect the operation
Follow the action provided by the page after entering the required input; check the field labels so source values and generated results are not confused. Review the complete output, not just its first line or summary. Check required fields, ordering, escaping, units, and warnings that could affect the next system in the workflow. If the result differs from an expected sample, change one input or option at a time so the cause remains clear.
Validate before integration
Use an independent check that matches the output’s destination: parse a generated document with its target parser, test a command in a safe environment, compare calculated values with known units, or verify a request against its API contract. A successful action confirms that the page completed its operation; it does not prove that the output fits every runtime, policy, or production environment.
Scope and practical limits
Use non-production examples where possible. Decoding or generating a value does not by itself verify a signature, secure an application, or replace a security review. Retain the original source until the receiving tool or service accepts the result. For an important change, record the input and options used so another developer can reproduce and review the same outcome. When results depend on project defaults, confirm them with a second representative input. If outputs differ unexpectedly, compare the source, options, and target environment before editing the result by hand; this makes the workflow easier to reproduce and review.