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nghttp - Man Page

HTTP/2 client


nghttp [Options]... <URI>...


HTTP/2 client


Specify URI to access.


-v,  --verbose

Print   debug   information   such  as   reception   and transmission of frames and name/value pairs.  Specifying this option multiple times increases verbosity.

-n,  --null-out

Discard downloaded data.

-O,  --remote-name

Save  download  data  in  the  current  directory.   The filename is  derived from  URI.  If  URI ends  with '/', 'index.html'  is used  as a  filename.  Not  implemented yet.

-t,  --timeout=<DURATION>

Timeout each request after <DURATION>.  Set 0 to disable timeout.

-w,  --window-bits=<N>

Sets the stream level initial window size to 2**<N>-1.

-W,  --connection-window-bits=<N>

Sets  the  connection  level   initial  window  size  to 2**<N>-1.

-a,  --get-assets

Download assets  such as stylesheets, images  and script files linked  from the downloaded resource.   Only links whose  origins are  the same  with the  linking resource will be downloaded.   nghttp prioritizes resources using HTTP/2 dependency  based priority.  The  priority order, from highest to lowest,  is html itself, css, javascript and images.

-s,  --stat

Print statistics.

-H,  --header=<HEADER>

Add a header to the requests.  Example: -H':method: PUT'


Add a trailer header to the requests.  <HEADER> must not include pseudo header field  (header field name starting with ':').  To  send trailer, one must use  -d option to send request body.  Example: --trailer 'foo: bar'.


Use  the specified  client certificate  file.  The  file must be in PEM format.


Use the  client private key  file.  The file must  be in PEM format.

-d,  --data=<PATH>

Post FILE to server. If '-'  is given, data will be read from stdin.

-m,  --multiply=<N>

Request each URI <N> times.  By default, same URI is not requested twice.  This option disables it too.

-u,  --upgrade

Perform HTTP Upgrade for HTTP/2.  This option is ignored if the request URI has https scheme.  If -d is used, the HTTP upgrade request is performed with OPTIONS method.

-p,  --weight=<WEIGHT>

Sets  weight of  given  URI.  This  option  can be  used multiple times, and  N-th -p option sets  weight of N-th URI in the command line.  If  the number of -p option is less than the number of URI, the last -p option value is repeated.  If there is no -p option, default weight, 16, is assumed.  The valid value range is [1, 256], inclusive.

-M,  --peer-max-concurrent-streams=<N>

Use  <N>  as  SETTINGS_MAX_CONCURRENT_STREAMS  value  of remote endpoint as if it  is received in SETTINGS frame.

Default: 100

-c,  --header-table-size=<SIZE>

Specify decoder  header table  size.  If this  option is used  multiple times,  and the  minimum value  among the given values except  for last one is  strictly less than the last  value, that minimum  value is set  in SETTINGS frame  payload  before  the   last  value,  to  simulate multiple header table size change.


Specify encoder header table size.  The decoder (server) specifies  the maximum  dynamic table  size it  accepts. Then the negotiated dynamic table size is the minimum of this option value and the value which server specified.

-b,  --padding=<N>

Add at  most <N>  bytes to a  frame payload  as padding. Specify 0 to disable padding.

-r,  --har=<PATH>

Output HTTP  transactions <PATH> in HAR  format.  If '-' is given, data is written to stdout.


Force colored log output.


Send large header to test CONTINUATION.


Don't send content-length header field.


Don't send dependency based priority hint to server.


Display the  incoming traffic in  hexadecimal (Canonical hex+ASCII display).  If SSL/TLS  is used, decrypted data are used.


Disable server push.


The  number of  concurrent  pushed  streams this  client accepts.


Perform an Expect/Continue handshake:  wait to send DATA (up to  a short  timeout)  until the server sends  a 100 Continue interim response. This option is ignored unless combined with the -d option.

-y,  --no-verify-peer

Suppress  warning  on  server  certificate  verification failure.


Enable ktls.


Disable RFC7540 priorities.


Display version information and exit.

-h,  --help

Display this help and exit.

The <SIZE> argument is an integer and an optional unit (e.g., 10K is 10 * 1024).  Units are K, M and G (powers of 1024).

The <DURATION> argument is an integer and an optional unit (e.g., 1s is 1 second and 500ms is 500 milliseconds).  Units are h, m, s or ms (hours, minutes, seconds and milliseconds, respectively).  If a unit is omitted, a second is used as unit.

Dependency Based Priority

nghttp sends priority hints to server by default unless --no-dep is used.  nghttp mimics the way Firefox employs to manages dependency using idle streams.  We follows the behaviour of Firefox Nightly as of April, 2015, and nghttp's behaviour is very static and could be different from Firefox in detail.  But reproducing the same behaviour of Firefox is not our goal.  The goal is provide the easy way to test out the dependency priority in server implementation.

When connection is established, nghttp sends 5 PRIORITY frames to idle streams 3, 5, 7, 9 and 11 to create "anchor" nodes in dependency tree:

         |id=0 |
        ^   ^   ^
 w=201 /    |    \ w=1
      /     |     \
     / w=101|      \
 +-----+ +-----+ +-----+
 |id=3 | |id=5 | |id=7 |
 +-----+ +-----+ +-----+
    ^               ^
w=1 |           w=1 |
    |               |
 +-----+         +-----+
 |id=11|         |id=9 |
 +-----+         +-----+

In the above figure, id means stream ID, and w means weight. The stream 0 is non-existence stream, and forms the root of the tree. The stream 7 and 9 are not used for now.

The URIs given in the command-line depend on stream 11 with the weight given in -p option, which defaults to 16.

If -a option is used, nghttp parses the resource pointed by URI given in command-line as html, and extracts resource links from it.  When requesting those resources, nghttp uses dependency according to its resource type.

For CSS, and Javascript files inside "head" element, they depend on stream 3 with the weight 2.  The Javascript files outside "head" element depend on stream 5 with the weight 2.  The mages depend on stream 11 with the weight 12.  The other resources (e.g., icon) depend on stream 11 with the weight 2.

See Also

nghttpd(1), nghttpx(1), h2load(1)


Tatsuhiro Tsujikawa

Referenced By

h2load(1), nghttpd(1), nghttpx(1).

May 19, 2024 1.62.1 nghttp2