Paste base64 or hexadecimal zlib data and decompress it into readable text.
Compression tool
Enter a value to see the result automatically.
Guide
Decompress Base64 or Hex zlib data online, compare compressed and output sizes, and automatically pretty-print decoded JSON with browser-native processing.
Zlib and deflate payloads appear in APIs, caches, logs, and encoded debugging samples. They are similar to gzip in that they compress bytes, but the wrapper format is different. A gzip decoder will often fail when the input is actually zlib data, which is why a separate focused page is useful.
This tool accepts base64 or even-length hexadecimal input and attempts to decompress it using the browser DecompressionStream API. When the decompressed result is text, it is shown directly in the output area. The page is designed for short pasted values rather than large archives.
A common use case is debugging an encoded field from an API response or a stored diagnostic value. You can paste the compressed text, run the decompressor, and quickly see whether the payload contains JSON, plain text, HTML, or another readable format.
If the output is unreadable, the original payload may be binary, encrypted, not actually zlib, or encoded in another wrapper. Try the gzip decompressor when you know the payload starts as gzip, and use this page for zlib or deflate-style data.
Quick reference
eJzzSM3JyVcozy/KSQEAGKsEPQ==
Input encoding: Base64 / Compression wrapper: Zlib / deflate / Compressed size: 19 bytes / Decompressed size: 11 bytes / Output: Hello world
Gzip, zlib, and raw deflate are related but not interchangeable. A payload can fail simply because it is using a different wrapper.
The page is designed for pasted base64 or hexadecimal strings, not large binary archives or files.
Decompression uses browser-native APIs when available. Older browsers may not expose the required stream support.
In-depth guide
Zlib, raw deflate, and gzip use related compression technology but different containers. Checking the expected wrapper and text encoding is the fastest way to diagnose a failed decode.
A zlib stream normally includes a short header and an Adler-32 checksum around deflate data. This differs from the larger gzip container.
Libraries sometimes use deflate to mean zlib-wrapped data and sometimes mean raw deflate blocks. Confirm the producer's documentation when decoding fails.
Both are text representations of the compressed bytes. This page detects either input form before applying browser-native decompression.
Compressed and decompressed byte counts help verify that a payload expanded as expected and make unexpectedly large output easier to notice.
Common mistakes
No. They are related compression formats, but their wrappers differ and they should be decoded with the right tool.
Yes. Even-length hexadecimal input is accepted.
The decompressed bytes may not be text, or the input may not be valid zlib data.
No. Both commonly contain deflate-compressed data, but their headers, checksums, and container formats differ.
Browser DecompressionStream deflate mode expects a compatible wrapped stream. Truly raw deflate data may require a library or producer-specific handling.
No. Base64 decoding only restores bytes. Zlib decompression is a separate step applied afterward.