OTC to GZ Converter
Processing entirely on your device — large files may take a moment.
OpenType Collection and Gzip Compressed File exist for different jobs: OTC is the CFF-flavored OpenType collection — the same ttcf container carrying PostScript-outline members instead of TrueType ones. Unpack a .gz into a normal file or repack it as ZIP/TAR when the receiving tool does not understand gzip.
This converter runs entirely in your browser using WebAssembly — your files never leave your device, nothing is uploaded, and there are no watermarks, sign-ups or queues. Drop in several files at once to convert them as a batch.
How to convert OTC to GZ
- 1
Select your files
Select your OTC file.
- 2
Convert instantly
The file bytes are gzip-compressed in place — the same archive your server or build tool produces, made locally.
- 3
Download results
Download the .gz file — ready to upload, serve or attach.
About the OTC format
TTC (TrueType Collection) is how you ship five CJK fonts in one download: a small ttcf header with member offsets points into shared glyph tables, so the fonts that differ only in metrics cost almost nothing extra. Microsoft's SimSun family and macOS system fonts are TTCs.
Most font tools want a single font, not a collection — extraction picks the first member and trims it to its own table directory, producing an ordinary TTF that every converter and @font-face rule accepts.
+Strengths
- ✓Shared glyphs make multi-font files small
- ✓Standard on Windows and macOS for CJK
- ✓First member extracts to a clean TTF
!Limitations
- −Most apps cannot use a collection directly
- −Web @font-face does not accept TTC
- −Members share glyphs — editing one is tricky
About the GZ format
A .gz file is one file squeezed by gzip — not an archive. kernel.org tarballs are “tar inside gz”, but plenty of logs, JSON dumps and CSV exports travel as plain .gz. Opening one means decompressing it back to the original bytes.
Repacking into ZIP or TAR gives the decompressed file a container that every GUI tool opens without a second thought.
+Strengths
- ✓Everywhere on Linux and macOS
- ✓Fast, well-understood compression
- ✓Streams natively from any tool
!Limitations
- −Single file only — no directory tree
- −No encryption or integrity metadata
Why convert OTC to GZ?
There is a concrete reason this conversion exists: Most apps cannot use a collection directly GZ sidesteps that — Everywhere on Linux and macOS If that is your situation, the tool above settles it in seconds, entirely on your device.
Frequently asked questions
Is this OTC to GZ converter really free?
Yes — completely free, with no sign-up, no watermark and no daily conversion limits. The site is supported by advertising.
Are my files uploaded to a server?
No. The conversion runs entirely inside your browser using WebAssembly, so your files never leave your device — that is what makes it instant and private.
Does it work on Windows, Mac, iPhone and Android?
Yes. Anything with a modern browser works: Windows, macOS, Linux, Android and iOS. No software installation is required.
Is there a file size limit for OTC to GZ?
The only limit is your device's memory, since nothing is uploaded. Files up to a few hundred megabytes work fine on a modern desktop browser; very large files simply take a little longer.
Are the files inside my OTC archive modified?
No. Contents are unpacked in memory and repacked into GZ byte-for-byte — the conversion changes the container, never the files inside it.
Is there a size limit for archive conversion?
There is no upload cap because nothing is uploaded — the practical limit is your device memory. A few hundred megabytes of unpacked content works comfortably on a modern computer.