Checksums vs Cryptographic Hashes
By qc_admin
Both turn data into a short fixed value, but a checksum catches accidents while a cryptographic hash resists attackers. Here is when to use each.
Author: qc_admin
base64url Explained: The URL-Safe Variant
By qc_admin
How base64url differs from standard Base64: the swapped + and / characters, dropped padding, why JWTs use it, and how to convert between the two variants safely.
301 vs 302 Redirects: What’s the Difference?
By qc_admin
When to use a 301 versus a 302, how caching and SEO differ, where 307 and 308 fit, and why the method-preserving codes exist.
What a JWT Actually Contains
By qc_admin
A JWT is three base64url parts: header, payload, and signature. Here is what each holds and why the payload is readable, not encrypted.
UUID v4 vs v7: What Changed and Why
By qc_admin
How UUIDs are structured, why v4 is fully random, how v7 embeds a millisecond timestamp for index locality, and the privacy tradeoff of a time-ordered ID.
URL Encoding: When It’s Needed and When It Breaks
By qc_admin
How percent-encoding works, reserved vs unreserved characters, encodeURIComponent vs encodeURI, %20 vs +, and the double-encoding bugs that break URLs.
Unix Timestamps and Timezone Handling
By qc_admin
A Unix timestamp counts seconds since 1970 UTC. Learn seconds vs milliseconds, UTC vs local, ISO 8601, and the accurate Year-2038 problem.
Regex Quantifiers: Greedy vs Lazy Matching
By qc_admin
Regex quantifiers *, +, ?, and {n,m} are greedy by default. Learn how adding ? makes them lazy, how backtracking works, with worked examples.
Redirect Rules: htaccess and nginx Compared
By qc_admin
Apache RewriteRule and Redirect versus nginx rewrite and return: 301 vs 302, regex backrefs, flags, and testing before you deploy.
Reading a Diff Properly
By qc_admin
How to read a unified diff: the @@ hunk header, + and – lines, context lines, line-level vs word-level diffs, and when to ignore whitespace.