How is this related to CSV Compressor?

It's the literal inverse. CSV Compressor gzips CSV text into real .csv.gz bytes via CompressionStream("gzip"); CSV Decompressor takes those same bytes and runs them back through DecompressionStream("gzip") to recover the original CSV text.

What's the difference between the file upload and the paste-base64 options?

The file upload path reads a real .csv.gz file's raw bytes directly via file.arrayBuffer() and gunzips them. The paste-base64 path is for when you only have a base64-encoded copy of those gzip bytes (for example, from CSV Compressor's copyable text output), it first decodes the base64 back into bytes, then runs the same gunzip step.

Why would I have a base64 string instead of a .csv.gz file?

Gzip output is binary, and some tools (including CSV Compressor's text panel here) show a base64 encoding of compressed bytes so they can be copied and pasted as text. The base64 path exists specifically to reverse that.

What happens if the file or text isn't actually gzip data?

DecompressionStream throws when the input isn't valid gzip, and the tool catches that and reports a friendly error asking whether the input is actually gzip-compressed, rather than a confusing browser exception.

CSV Decompressor - Gunzip a .csv.gz File Back to CSV Text

Overview

Introduction

If you've got a .csv.gz file, whether from CSV Compressor or anywhere else, you eventually need to look at the CSV text inside it. This tool gunzips it entirely in your browser.

It handles two real-world cases: a real .csv.gz file you can drop in directly, or a base64 text copy of those same gzip bytes that you need decoded back to bytes first.

What Is CSV Decompressor?

A gzip decompressor built on the Web Platform's native DecompressionStream("gzip") API, the literal inverse of CSV Compressor's CompressionStream("gzip") step.

It accepts input two ways: a direct .csv.gz file upload, or a pasted base64-encoded string representing the same compressed bytes, both end up decompressed into the same plain CSV text output.

How CSV Decompressor Works

For a file upload, the browser's File object is read into raw bytes via arrayBuffer(), then piped through DecompressionStream("gzip") using the same ReadableStream/Response pipeline pattern CSV Compressor uses in reverse.

For pasted base64, the text is first decoded back into bytes with atob() and Uint8Array.from(), then handed to the exact same gunzip step, so both paths converge on identical decompression logic.

When To Use CSV Decompressor

Use this whenever you have a .csv.gz file and need to see or edit the CSV text inside it without a command-line gunzip.

It's also the natural pairing for CSV Compressor's base64 text output, when you want to verify round-tripping without ever leaving the browser.

Often used alongside CSV Compressor.

Features

Advantages

Runs entirely client-side using a native browser API, your compressed data never leaves your machine.
Handles both a real binary .csv.gz upload and a base64 text paste, covering how gzip data actually shows up in practice.
Reports a clear, friendly error instead of a raw exception when the input isn't valid gzip.

Limitations

Only understands gzip-format compression, not zip, brotli, or other archive formats.
Very large decompressed CSVs are held fully in memory as a single string, which can be slow for extremely large files.

Examples

Round-tripping with CSV Compressor

Input

(a .csv.gz file downloaded from CSV Compressor)

Output

id,status
1,active
2,active
3,active
4,inactive

Uploading the .csv.gz file recovers the exact original CSV text, since gzip decompression is lossless.

Best Practices & Notes

Best Practices

Use the file upload path whenever you actually have a .csv.gz file, it's the more direct route.
Reach for the base64 paste path only when you specifically have a base64 text copy of gzip bytes, not a real file.
If decompression fails, double check the file extension and that the base64 text wasn't truncated when copied.

Developer Notes

decompressGzipBytes() pipes a Uint8Array through `new DecompressionStream("gzip")` inside a `ReadableStream`/`Response` pipeline (the mirror image of csv-compressor.ts's gzip() helper) and reads the result back as text via Response.text(); decompressBase64Gzip() decodes base64 to bytes with `Uint8Array.from(atob(base64), c => c.charCodeAt(0))` first, then delegates to decompressGzipBytes(), and both paths report a friendly error string rather than letting the DecompressionStream exception propagate.

CSV Decompressor Use Cases

Recovering the original CSV text from a .csv.gz file without a command-line tool
Verifying a CSV Compressor round trip by decompressing what it just compressed
Decoding a base64 copy of gzip bytes (pasted from elsewhere) back into readable CSV

Common Mistakes

Pasting a .csv.gz file's raw bytes as text into the base64 box, that box expects base64-encoded text, not raw binary.
Assuming any upload failure means the file is corrupted, sometimes it just isn't gzip data at all (e.g. a plain .csv renamed to .csv.gz).

Tips

Keep CSV Compressor's base64 output panel open in another tab if you're testing a round trip, it's a fast way to generate valid input here.
Once decompressed, send the CSV straight into CSV Editor to start making changes.

CSV Decompressor