How to use download compression in wget

HTTP compression reduces the number of bytes transferred for text responses such as plain-text documents, JSON payloads, and generated reports. That usually matters most on slower links or repetitive scripted downloads where the payload compresses well.

In wget, --compression=auto and --compression=gzip ask the server for gzip-compressed HTTP content, and wget expands the response back into a normal local file when the server replies with Content-Encoding: gzip. --compression=none leaves compression negotiation off.

Use compression for text-heavy HTTP downloads, not for archives or checksum-sensitive transfers where you need the exact bytes sent on the wire. Servers can also ignore the request, so the transfer is only compressed when the remote endpoint chooses to send a compressed response.

1. Confirm that the local wget build supports compression control and note the default mode.

   $ wget --help
   ##### snipped #####
          --compression=TYPE          choose compression, one of auto, gzip and none. (default: none)
   ##### snipped #####

   The default none mode means wget will not ask the server for compressed HTTP content until you enable it explicitly.

2. Download a text file with compression enabled and inspect the server response.

   $ wget --compression=auto --server-response --output-document=gpl-3.0.txt https://www.gnu.org/licenses/gpl-3.0.txt
   --2026-04-22 10:31:03--  https://www.gnu.org/licenses/gpl-3.0.txt
   Resolving www.gnu.org (www.gnu.org)... 209.51.188.116, 2001:470:142:5::116
   Connecting to www.gnu.org (www.gnu.org)|209.51.188.116|:443... connected.
   HTTP request sent, awaiting response...
     HTTP/1.1 200 OK
     Date: Wed, 22 Apr 2026 02:31:04 GMT
     Server: Apache
     Strict-Transport-Security: max-age=63072000
     X-Frame-Options: sameorigin
     X-Content-Type-Options: nosniff
     Access-Control-Allow-Origin: (null)
     Last-Modified: Sat, 30 Sep 2017 07:16:26 GMT
     ETag: "894d-55a62eb645dcd-gzip"
     Accept-Ranges: bytes
     Vary: Accept-Encoding
     Content-Encoding: gzip
     Content-Length: 12130
     Keep-Alive: timeout=5, max=100
     Connection: Keep-Alive
     Content-Type: text/plain
     Content-Language: non-html
   Length: 12130 (12K) [text/plain]
   Saving to: 'gpl-3.0.txt'
   
        0K .......... .                                          100% 12.7M=0.001s
   
   2026-04-22 10:31:04 (12.7 MB/s) - 'gpl-3.0.txt' saved [35149]

   The Content-Encoding: gzip header confirms the transfer was compressed, while the larger saved byte count shows that wget expanded the file back into plain text on disk.

3. Confirm that the saved file is ordinary text after the download completes.

   $ file gpl-3.0.txt
   gpl-3.0.txt: ASCII text

4. Compare the same URL with compression disabled.

   $ wget --compression=none --server-response --output-document=gpl-3.0-plain.txt https://www.gnu.org/licenses/gpl-3.0.txt
   --2026-04-22 10:31:21--  https://www.gnu.org/licenses/gpl-3.0.txt
   Resolving www.gnu.org (www.gnu.org)... 209.51.188.116, 2001:470:142:5::116
   Connecting to www.gnu.org (www.gnu.org)|209.51.188.116|:443... connected.
   HTTP request sent, awaiting response...
     HTTP/1.1 200 OK
     Date: Wed, 22 Apr 2026 02:31:22 GMT
     Server: Apache
     Strict-Transport-Security: max-age=63072000
     X-Frame-Options: sameorigin
     X-Content-Type-Options: nosniff
     Access-Control-Allow-Origin: (null)
     Last-Modified: Sat, 30 Sep 2017 07:16:26 GMT
     ETag: "894d-55a62eb645dcd"
     Accept-Ranges: bytes
     Content-Length: 35149
     Vary: Accept-Encoding
     Keep-Alive: timeout=5, max=100
     Connection: Keep-Alive
     Content-Type: text/plain
     Content-Language: non-html
   Length: 35149 (34K) [text/plain]
   Saving to: 'gpl-3.0-plain.txt'
   
        0K .......... .......... .......... ....                 100%  149K=0.2s
   
   2026-04-22 10:31:22 (149 KB/s) - 'gpl-3.0-plain.txt' saved [35149/35149]

   No Content-Encoding header and matching transfer and saved sizes mean the server sent the plain response without gzip compression.

   Add --debug when you need to inspect the request itself. Current GNU Wget sends Accept-Encoding: gzip with auto or gzip, and Accept-Encoding: identity with none.

5. Remove the temporary files after the test.

   $ rm gpl-3.0.txt gpl-3.0-plain.txt

   Use --compression=none for archive downloads or checksum comparisons where transparent decompression would change the saved bytes.