Check Cloudflare _redirects before deployment — browser-only preflight

[yuya-msd]

Maintaining a _redirects file for Pages or Workers Static Assets? This small, independent checker gives source-linked, line-specific diagnostics for documented file constraints.

Open the checker — no signup or payment.

Try it on your next pre-deploy check

1. Paste a non-sensitive _redirects file, or select Choose local file.
2. Select Run preflight and review the diagnostics and linked official sources.
3. If useful, select Export JSON report to save a local copy.

There is also a clearly labelled synthetic sample for exploring the interface. The optional task selector and usefulness buttons can be left unanswered; please choose only what accurately describes your task.

A concrete example

These are synthetic rules, not a user's deployment:

/old /new 301
/blog/* /archive/:splat 302
/api/* https://api.example.com/:splat 200

The first two have no blocking issue in this checker. The third is flagged because Cloudflare documents 200 proxying to a relative destination on the same site, not to an external domain. This is a file-level diagnostic, not a test of those URLs.

Checks include documented syntax, status codes, rule counts and declaration length, ordering and destination placeholders. Results distinguish confirmed errors, warnings, potential issues and unknowns.

Scope and privacy

It does not execute Cloudflare's production parser, fetch destination URLs, inspect account settings, or resolve framework output paths and Bulk Redirect interactions. Pages Functions and requests served by Worker code need separate review. Order-dependent budget behavior is treated conservatively rather than emulated. A clean report does not guarantee routing or deployment success.

Rule text and filenames are not sent by the app. The public experiment records limited categorical usage events with a temporary tab-session ID, not a persistent visitor ID. Cloudflare still processes normal infrastructure request metadata. Privacy notice. Please do not paste secrets or share private rules in this thread. The page's Traffic/Conversion labels are static placeholders, not live usage counters.

Official references: Pages redirects and Workers Static Assets redirects.

For people who actually maintain these files: did it catch something useful, miss something important, or add no value over Wrangler and the docs? Any of those is useful feedback; no private file or path is needed.

The tool and this post were developed with AI assistance. This is an independent project, not an official Cloudflare tool.