CodExtension is a file-format library and a set of small tools. The library says what a file really is; the tools read it without the application that produced it. Nothing is uploaded and nothing is installed to look at a file.
The site began in 2004 as a studio: design templates, CMS extensions for Joomla, WordPress, Drupal and MooTools, and a service that took a Photoshop layout and built a working template out of it. That ended in 2023. What is here now grew out of the support mail — almost every ticket was some version of this file will not open.
What is here
- The file library — one page per format, starting with the header rather than the marketing name.
- Conversion guides — short guides that name the settings worth keeping.
- Tools — signature check, checksums, archive peek, EPS repair and the rest.
- Error codes — the codes people paste into support mail.
- Drivers — printer and scanner drivers, and what the generic driver leaves out.
- Design archive — the template and layout files the studio used to ship.
Why the library starts with the bytes
An extension is a label somebody chose. The first bytes of a file are a record of what the writing application actually did. Six bytes are usually enough to name the format: Photoshop writes 8BPS, a PDF writes %PDF-, a ZIP — and therefore a DOCX, an EPUB or an APK — writes PKx03x04, and AutoCAD writes a release code such as AC1032. That is where every format page begins.
New format pages go up weekly. The index is rebuilt with each batch.
Reviewed 2026-10-05 by M. Halvorsen.