What does it do?
It compresses text with gzip, deflate (zlib) or raw deflate and gives you the result in Base64, and it decompresses Base64 payloads back to text. Typical uses:
- Reading compressed API payloads, cookies or JWT claims that someone gzipped to save space.
- Inspecting values stored compressed in databases, logs or message queues.
- Checking how much a JSON response would shrink with compression.
How to use it
- Paste text to compress it; the sizes before and after and the savings appear above the result.
- Press Swap to decompress Base64. Leave the format on Auto-detect unless you know it.
- Data URLs and Base64URL are accepted too.
Small inputs may grow after compression because of the format's headers: compression pays off from a few hundred bytes of repetitive data.
Frequently asked questions
›How do I know if a Base64 string is gzip?
Gzip data always starts with the bytes 1F 8B, so its Base64 starts with H4sI. Zlib (deflate) usually starts with eJ. Auto-detect uses those signatures.
›What is the difference between gzip, deflate and deflate-raw?
All three use the same DEFLATE algorithm. gzip adds a header and a CRC32 checksum, deflate (zlib) adds a smaller header and an Adler-32 checksum, and deflate-raw has no header at all.
›Is it the same compression the web server uses?
Yes: Content-Encoding: gzip and deflate use exactly these formats, through the browser's native CompressionStream API.