varnishlog

Display Varnish HTTP request logs

TLDR

Show live logs

$ varnishlog

Include only specific tag

$ varnishlog -i [ReqURL]

Filter by query

$ varnishlog -q "[RespStatus == 500]"

Client requests only

$ varnishlog -c

Backend requests only

$ varnishlog -b

Group by request

$ varnishlog -g request

SYNOPSIS

varnishlog [-c] [-b] [-q query] [-i tag] [options]

varnishlog reads the Varnish Shared Memory Log (VSL) and displays detailed request and response information in real time. It shows the full lifecycle of HTTP transactions including client requests, backend fetches, cache decisions, and response headers.The tool provides powerful filtering through the VSL query language, allowing you to isolate specific transactions by status code, URL pattern, or any logged field. Client-side (-c) and backend-side (-b) views can be shown independently, and grouping modes organize output by request, session, or raw log entries. This makes it the primary debugging tool for understanding Varnish cache behavior.

PARAMETERS

-c

Show client-side transactions only.

-b

Show backend-side transactions only.

-q QUERY

VSL query expression to filter transactions.

-i TAGLIST

Include only records with specified tags (comma-separated).

-I TAGREGEX

Include only records matching tag and regex pattern.

-x TAGLIST

Exclude records with specified tags.

-X TAGREGEX

Exclude records matching tag and regex pattern.

-g MODE

Grouping mode (raw, vxid, request, session).

-d

Process old log entries first.

-w FILENAME

Write output to file.

INSTALL

sudo apt install varnish

sudo dnf install varnish

sudo apk add varnish

brew install varnish

nix profile install nixpkgs#varnish

CAVEATS

Requires a running Varnish instance. Familiarity with VSL query language is helpful for effective filtering. Output can be very verbose without filters.

HISTORY

varnishlog is part of Varnish Cache, displaying the Varnish Shared Memory Log for debugging.