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The Zlib compressor uses the deflate algorithm to compress text data and encodes the result as Base64 for easy storage and transmission. It also decompresses Base64-encoded zlib data back to plain text.

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Features

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Deflate compression

Uses the industry-standard deflate algorithm (the same compression used in ZIP files and gzip) via the fflate library for efficient compression.

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Base64 output

Compressed data is automatically Base64-encoded, making it:
  • Safe for text-based storage
  • Easy to transmit over HTTP
  • Compatible with JSON and XML
  • Suitable for embedding in HTML or CSS

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Compression statistics

After compressing or decompressing, view detailed statistics: For compression:
  • Input size in bytes
  • Output size in bytes (compressed)
  • Compression ratio as a percentage
For decompression:
  • Input size in bytes (compressed Base64)
  • Output size in bytes (decompressed text)
  • Expansion percentage

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Bidirectional operation

Switch between compress and decompress modes using tabs:
  • Compress - Takes plain text and outputs compressed Base64
  • Decompress - Takes compressed Base64 and outputs plain text

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Error handling

Clear error messages for:
  • Invalid compressed data format
  • Corrupted Base64 input
  • Decompression failures

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Tool cross-linking

Quick navigation to the Base64 tool for scenarios where you need encoding without compression.

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Keyboard shortcuts

Speed up your workflow:
  • Execute compression or decompression
  • Copy output to clipboard
  • Clear all fields

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Use cases

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Reducing payload size

Compress large JSON or XML data before sending it over the network: 
Input: Large configuration file (1000 bytes)
Output: Compressed Base64 string (450 bytes)
Compression ratio: 55%

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Storing configuration data

Compress and encode configuration strings to reduce storage requirements in databases or local storage.

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URL shortening

Compress long state data before encoding it in a URL parameter.

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Log compression

Compress verbose log messages before transmission to a logging service.

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Text backup

Create compressed backups of text content that can be safely stored or transmitted.
Compression works best on repetitive or structured text. Random data, encrypted data, or already-compressed formats may not compress well.

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How it works

Compression process:
  1. Convert input text to UTF-8 bytes using strToU8()
  2. Apply deflate compression using deflateSync()
  3. Convert compressed bytes to Base64 string
  4. Calculate compression statistics
  5. Display the result with metrics
Decompression process:
  1. Decode Base64 string to bytes
  2. Apply inflate decompression using inflateSync()
  3. Convert bytes back to UTF-8 string using strFromU8()
  4. Calculate decompression statistics
  5. Display the original text
For best compression ratios, use this tool on structured data like JSON, XML, or repetitive text rather than on random strings or pre-compressed data.

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Understanding compression ratios

The compression ratio shows how much smaller (or larger) the output is compared to the input:
  • Positive ratio (e.g., +55%) - Data compressed by 55%
  • Negative ratio (e.g., -15%) - Data expanded by 15% (compression not beneficial)
  • Near-zero ratio - Data size remained similar
Very short text (under 100 bytes) often has negative compression ratios because the compression overhead exceeds the space savings.

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When to use Base64 vs Zlib

Use Base64 encoder when:
  • You need to encode binary data or text without compression
  • File size is not a concern
  • You want faster processing
  • Compatibility is the primary goal
Use Zlib compressor when:
  • You need to reduce data size significantly
  • You’re working with large, repetitive, or structured text
  • Network bandwidth or storage space is limited
  • The overhead of compression/decompression is acceptable
  • Base64 encoder - For encoding without compression
  • URL encoder - For percent-encoding compressed data in URLs

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