Developer Guides

A practical engineering guide to API authentication. Understand API keys, Basic auth, Bearer tokens, OAuth 2.0, JWT, HMAC request signing, and mutual TLS — and when to use each.

A JWT is just Base64 — anyone can read it. What that means for inspecting tokens safely, why pasting a live token into a random website is risky, how signature verification actually protects you, and what belongs in a token.

What actually happens when you upload a PDF to an online tool — server retention, breach exposure, and jurisdiction — and how in-browser PDF editing avoids it. With a practical way to verify any tool yourself.

Whether a web password generator is safe comes down to one thing: does the password get created in your browser, or on a server? How to tell the difference, the real threat model, and what matters more than where the password is generated.

What a checksum is, how to verify a downloaded file's SHA-256 hash on macOS, Windows, and Linux, what it actually catches, and the limit of trusting a hash published next to the file.

A step-by-step guide to redacting images safely: black box vs blur vs pixelate, why destructive redaction matters, how to also strip the metadata, and a ten-second check that nothing was uploaded.

A complete, practical comparison of modern image formats. Understand AVIF, WebP, JPEG XL, and the classics (JPEG, PNG, GIF), their compression, browser support, and exactly when to use each.

A practical guide to diffing: how a diff tool finds changes, line vs word vs character diffs, reading added and removed lines, and comparing configs, code, and contracts without uploading them.

The gray-middle problem in CSS gradients explained: why sRGB interpolation dulls the midpoint, and three fixes — a midpoint color stop, modern interpolation color spaces like oklch, and choosing harmonious endpoints.

We classified all 180 tools on UseToolSuite by the browser capability that lets each one run without a server. The result is a concrete snapshot of what no longer needs a backend in 2026 — files, crypto, even ML.

How to fill interactive PDF forms in your browser: completing AcroForm fields, why flattening matters before you send, what to do with flat or scanned forms, and keeping personal documents off third-party servers.

A practical guide to generating QR codes that actually scan: the four error-correction levels and when each matters, why more data makes a denser code, static vs dynamic codes, and testing before you print.