9 guides
Guides
Short, practical explanations of file-format problems, each with sample files to reproduce them.
All guides
How to test file uploads properly
A practical checklist for testing upload forms and APIs — size limits, empty files, content-type validation, file names and interrupted transfers.
How to create a test file of any size (1 GB, 2 GB, 4 GB and more)
One-line commands for macOS, Linux and Windows that create exact-size test files, why random data beats zeros for upload tests, and which sizes break software.
MP4 vs WebM vs MOV: which video format to use
Containers versus codecs, what each browser plays, and a practical default for web video in 2026.
Why your uploaded photos appear sideways (EXIF orientation)
How cameras store rotation in EXIF metadata, why images still show up rotated, and how to handle all eight orientations correctly.
Fixing CSV encoding problems: BOM, UTF-16, Latin-1 and more
Why CSV imports show garbled characters or a strange first column, and how to detect and handle each encoding Excel and legacy systems produce.
Extracting user-uploaded archives safely
Path traversal, symlink escapes, compression bombs and nested archives — what your extraction code must handle, and safe test files for the rest.
PNG vs JPEG vs WebP vs AVIF: which image format to use
How the four main web image formats differ in compression, transparency, animation and browser support, and a practical way to choose.
CSV vs JSON vs Parquet: choosing a data format
When plain text is enough and when a columnar binary format pays off — size, speed, types and tooling compared, with the same dataset in each format.
ZIP vs 7z vs tar.gz vs zst: which archive format to use
Compression ratio, speed, encryption and compatibility of the common archive formats, and which one to pick for downloads, backups and data.