Is there a way to use browser's native gzip decompression using Javascript?

Question

The backend server responds with a gzip file but without the Content-Encoding: gzip header . And I do not have control over the server so can't handle the issue server side.

What I need now is to decompress the gzipped file client side using javascript.

I have found this excellent library which can help me do this: http://nodeca.github.io/pako/

But I don't want to add additional library just to un-gzip a file. I feel that there should be a way to use the browser's native functionality to un-gzip. Am I correct? If I am wrong can someone explain why this browser functionality is not exposed as a javascript API? And is there a way to un-gzip a file in javascript without adding an additional library?

Answer 1

The Compression Streams API is a new web standard and is currently available in Chrome ( since v80 ). Other browsers will eventually add it, but in the mean time the best bet is a WASM implementation . Apparently WASM implementations can approach 90% of the performance of a native implementation (and ~20x the speed of a JS implementation).

Some example usage of the Compression Streams API:

async function decompressBlob(blob) {
  let ds = new DecompressionStream("gzip");
  let decompressedStream = blob.stream().pipeThrough(ds);
  return await new Response(decompressedStream).blob();
}

const compressedReadableStream = inputReadableStream.pipeThrough(new CompressionStream('gzip'));

More info:

• WICG standards doc

Answer 2

I feel that there should be a way to use the browser's native functionality to un-gzip. If I am wrong can someone explain why this browser functionality is not exposed as a javascript API?

No, there shouldn't be, unless it is in w3c standard and it is not. The only standard which says something about gzip compression is an HTTP standard .

I really believe it won't become standard because there are thousands of algorithms (for compression, encryption, etc.) which you may want to use and browsers cannot handle them all; it would also be unfair to create interfaces for one algorithm while not creating them for another.

HTTP protocol is a kind of exception. The compression here is done to make the life of millions of people easier. The HTTP is a bottle neck in web performance, so as long as the compression is available there I cannot imagine any case when you elsewhere need to use a compression in JavaScript. The only case I know is compressing items in a localStorage / indexedDB , but even there gzip won't work because it is not producing UTF-16 output.

That is why this is not in the standard and this is why it most likely won't appear there.

Your particular case is a server side implementation error. Using compressed output without a proper header really smells. Either don't use the compression or do it right.

And is there a way to un-gzip a file in javascript without adding an additional library?

Actually other than that there is a possible solution: create a browser extension which injects a proper header in a server response and you won't need a library but will need to distribute the extension to the users. Could be even worse, but still may work.