The Everyday Developer Cheat-Sheet: JSON, Base64, JWT, Cron, Regex

Five utilities cover 90% of a working developer's daily friction. Here's each one — what it does, the gotcha everyone hits, and a free tool that runs entirely in your browser.

JSON: format, minify, validate

JSON has exactly four rules that trip people up: double quotes only (no singles), no trailing commas, no comments, and true/false/null are lowercase (Python's True/None will fail). Paste suspect JSON into a JSON formatter/validator — good ones pinpoint the exact line and column of the first error, which beats staring at a 4,000-line config.

Base64: encoding, not encryption

Base64 converts binary into 64 safe text characters — that's all. It hides nothing (anyone can decode it), so never "protect" secrets with it. The classic bug: naive encoders break on non-Latin text because they skip UTF-8. A proper Base64 encoder/decoder handles emojis and Urdu/Chinese by encoding through UTF-8 first. You'll also meet URL-safe Base64 in JWTs, where +// become -/_ and padding is dropped.

JWT: decode, but never trust blindly

A JWT is three Base64URL parts: header (algorithm), payload (claims), signature. Decoding just reads it — verification requires the signing key on a server. The claim everyone should check: exp (expiry, a Unix timestamp in seconds). Paste a token into our JWT decoder to see claims with human-readable dates and a live "valid for / expired" verdict. Rule: never paste production tokens into tools you don't trust — ours decodes locally, but the habit matters everywhere.

Cron: five fields, one headache

Cron format: minute hour day-of-month month day-of-week. The expressions worth memorizing: */5 * * * * (every 5 minutes), 0 9 * * 1 (Mondays 9am), 0 0 1 * * (midnight on the 1st). Build and sanity-check any schedule with the cron generator — it explains your expression in plain English so a typo can't silently schedule 3 AM daily instead of 3 PM.

Regex: learn five patterns, cover 80%

• \d+ — digits (IDs, counts).
• \w+@\w+\.\w+ — quick-and-dirty email shape.
• ^\s+$ — whitespace-only lines (cleanup).
• (cat|dog) — alternatives; add g flag for all matches.
• \bword\b — whole-word find/replace.

Test live with match highlighting and capture groups in the regex tester — safer than experimenting in production logs.

The 10-second workflow

Bookmark these six: JSON, Base64, JWT, cron, regex, UUID. All local, all free, no signup — the way dev tools should be.