A tar file has no signature at byte 0 — ustar lives at 257
Why some tools call a tar file ‘unknown’ and how to tell a POSIX tar from a GNU one.
Guides
Why HEIC files show blank in Windows, and what to do about it
It is a missing codec, not a broken photo. Three ways to make HEIC display, plus the conversion that keeps 10-bit depth.
PSD clamps at 30,000 x 30,000 px — PSB exists for what is bigger
Gigapixel panoramas and layered files over 2 GB are written as .psb, and most readers handle both.
The checkbox that decides whether anyone can open your .ai file
‘Create PDF Compatible File’ is the difference between a file a client can look at and a file only Illustrator can read.
New camera bodies, old decoders: the raw support gap
CR3, newer ARW compression and X-Trans demosaicing all need decoders newer than the camera’s release.
The six bytes at the start of a DWG tell you which AutoCAD can open it
AC1032, AC1027, AC1021: the header code names the release. This turns a support ticket into a five-second check.
An EPS without a BoundingBox comment will not import
The comment is how a DTP package places the graphic. Here is how to rebuild it.
Reading a file’s first bytes is faster than guessing its extension
Every renamed file keeps the signature of the format it was written in. Six bytes are usually enough to name the real format.