Tutorials, deep-dives, and privacy-first thinking about developer tools.
Showing 73–84 of 111 posts
Batch convert 50 images to WebP, AVIF, JPG, or PNG at once, entirely in your browser — no upload, no sign-up, and your files never leave your device.
Unix timestamp 1700000000 was Tuesday, November 14, 2023, 22:13:20 UTC. Learn how to date any timestamp from its leading digits, no converter needed.
Convert any date to a Unix timestamp in Bash, Python, JavaScript, and SQL with copy-paste one-liners — plus the timezone trap each language hides.
Learn how to convert JPG to PNG in your browser, why it never restores lost quality, and the three cases where converting actually helps instead of bloating files.
JWT exp, nbf, and iat are Unix timestamps in seconds. Learn to read them in 3 seconds, convert them to a date, and check token expiry by hand.
Learn what the JWT exp, nbf, and iat claims mean, how to read token expiry without doing epoch math by hand, and the clock-skew gotchas that bite in 2026.
Your JavaScript timestamp is in milliseconds while most backends use seconds, so it looks 1000× too big. Here is why, and how to convert it safely.
Sign a JWT in the browser with HS256 and the Web Crypto API — five lines of JavaScript, no library, no server. The 2026 walkthrough.
When an API returns 401 Unauthorized in 2026, the JWT is usually the smoking gun. Decode the token, read exp, aud, iss — and fix the bug in 90 seconds.
Converting a Unix timestamp to a date is one division operation, but the timezone you format it in is the whole bug. Here's how to get it right.
RFC 3986 names just 66 characters as unreserved — and most encoders mishandle the rest of printable ASCII. Here's what each one actually is, and why it matters.
The JWT alg: none vulnerability lets attackers forge tokens without a secret. Here's how the exploit works and why libraries still trip on it in 2026.