Home > Uncategorized > H4sIAAA What’s so important about this string?

H4sIAAA What’s so important about this string?


This may be a long shot, but if anyone ever searches for this string, I know exactly what you are looking at – It’s a base64 encoded zipped string.

Want to see what it actually it, base64 decode the sting, and unzip the result, here’s the code you need in c#

public static void CopyTo(Stream src, Stream dest)
byte[] bytes = new byte[4096];

int cnt;

while ((cnt = src.Read(bytes, 0, bytes.Length)) != 0)
dest.Write(bytes, 0, cnt);

public static byte[] Zip(string str)
var bytes = Encoding.UTF8.GetBytes(str);

using (var msi = new MemoryStream(bytes))
using (var mso = new MemoryStream())
using (var gs = new GZipStream(mso, CompressionMode.Compress))
CopyTo(msi, gs);

return mso.ToArray();

public static string Unzip(byte[] bytes)
using (var msi = new MemoryStream(bytes))
using (var mso = new MemoryStream())
using (var gs = new GZipStream(msi, CompressionMode.Decompress))
CopyTo(gs, mso);

return Encoding.UTF8.GetString(mso.ToArray());

Categories: Uncategorized
  1. December 7, 2016 at 4:07 pm

    To help google, here’s some related markers


  2. Developer
    July 17, 2017 at 7:27 am

    after 7 months of your post, i had the same problem and your post helped me solving it. Thanks for your post 🙂

  3. Roland
    February 9, 2018 at 4:44 pm

    You don’t need to write a single line of code if you have access to a UNIX shell. With the encoded string sitting in “inputfile” in the current folder:

    base64 -Di inputfile|zcat

  4. May 29, 2021 at 6:15 am

    Currently working on reverse engineering a website to create a web crawler.

    Thank you so much for making this post, you saved me quite the headache.

    As a side note people might find this site useful to take a quick look at the data without opening up an IDE, I found it after reading this post and also noticed that it was able to detect the file type after I had decoded the Base64 – https://gchq.github.io/CyberChef/#recipe=From_Base64('A-Za-z0-9%2B/%3D‘,true)Unzip(”,false)

    I don’t have any affiliation with that site by the way, just ended up finding it useful for this situation and others may find it helpful as well.

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