Web Page Replay

Web Page Replay (WprGo) is a performance testing tool written in Golang for recording and replaying web pages. WprGo is currently used in Telemetry for Chrome benchmarking purposes. This requires go 1.8 and above. This has not been tested with earlier versions of go. It is supported on Windows, MacOS and Linux.


There are two ways to setup your GOPATH. The first is to use the go get command to fetch this directory. This will use your default GOPATH, which is typically $HOME/go:

go get github.com/catapult-project/catapult/web_page_replay_go

You can then find this directory in:


The second approach is to use your current catapult checkout. Assuming your “catapult” directory is located at $CATAPULT, and assuming $HOME/go is in your GOPATH, create the following symbolic link:

mkdir -p $HOME/go/src/github.com/catapult-project
ln -s $CATAPULT $HOME/go/src/github.com/catapult-project/catapult

If you take this second approach, you will need to manually fetch the required packages:

go get github.com/urfave/cli
go get golang.org/x/net/http2

Sample usage

Record mode

  • Terminal 1:

    Start wpr in record mode.

    go run src/wpr.go record --http_port=8080 --https_port=8081 /tmp/archive.wprgo



  • Terminal 2:

    google-chrome-beta --user-data-dir=$foo \
     --host-resolver-rules="MAP *:80,MAP *:443,EXCLUDE localhost"

    ... wait for record servers to start

Replay mode

  • Terminal 1:

    Start wpr in replay mode.

    cd path/to/web_page_replay_go
    go run src/wpr.go replay --http_port=8080 --https_port=8081 /tmp/archive.wprgo
  • Terminal 2:

    google-chrome-beta --user-data-dir=$bar \
     --host-resolver-rules="MAP *:80,MAP *:443,EXCLUDE localhost"

    ... wait for replay servers to start

    load the page

Running on Android

You will need a Linux host machine and an android device.

  • Set up reverse port forwarding
adb reverse tcp:8080 tcp:8080
adb reverse tcp:8081 tcp:8081
  • Set up command line arguments
build/android/adb_chrome_public_command_line --host-resolver-rules="MAP *:80,MAP *:443,EXCLUDE localhost" \
  • Run wpr.go as usual on the linux machine

(Optional) Installing test root CA

WebPageReplay uses self signed certificates for Https requests. To make Chrome trust these certificates, you can use --ignore-certificate-errors-spki-list like above. If that doesn't work, you may try installing a test certificate authority as a local trust anchor. Note: Please do this with care because installing the test root CA compromises your machine. This is currently only supported on Linux and Android.

Installing the test CA. Specify a --android_device_id if you'd like to install the root CA on an android device.

go run src/wpr.go installroot

Uninstall the test CA. Specify a --android_device_id if you'd like to remove the root CA from an android device.

go run src/wpr.go removeroot

Other use cases

Http-to-http2 proxy:

  • Terminal 1:
go run src/wpr.go replay --https_port=8081 --https_to_http_port=8082 \
  • Terminal 2:
google-chrome-beta --user-data-dir=$foo \
  --host-resolver-rules="MAP *:443,EXCLUDE localhost" \
  --ignore-certificate-errors-spki-list=PhrPvGIaAMmd29hj8BCZOq096yj7uMpRNHpn5PDxI6I= \
  --proxy-server=http= \

Inspecting an archive

httparchive.go is a convenient script to inspect a wprgo archive. Use ls,cat and edit. Options are available to specify request url host (--host) and path (--full-path).


go run src/httparchive.go ls /tmp/archive.wprgo --host=example.com --full-path=/index.html

Running unit tests

Run all tests in a specific file.

go test transformer_test.go transformer.go

Run all tests in webpagereplay module.

go test webpagereplay -run ''

Generate public key hash for --ignore-certificate-errors-spki-list

wpr_public_hash.txt is generated from wpr_cert.pem using the command below.

openssl x509 -noout -pubkey -in wpr_cert.pem | \
openssl pkey -pubin -outform der | \
openssl dgst -sha256 -binary | \


Please read contributor's guide. We use the Catapult issue tracker for bugs and features. Once your change is reviewed and ready for landing, please run telemetry/bin/update_wpr_go_binary to update binaries in Google cloud storage.


Please email telemetry@chromium.org.