lychee(1) General Commands Manual lychee(1)

lychee - A fast, async link checker

lychee [-a|--accept] [--accept-timeouts] [--archive] [-b|--base-url] [--base] [--basic-auth] [-c|--config] [--cache] [--cache-exclude-status] [--cookie-jar] [--default-extension] [--dump] [--dump-inputs] [-E|--exclude-all-private] [--exclude] [--exclude-file] [--exclude-link-local] [--exclude-loopback] [--exclude-path] [--exclude-private] [--extensions] [-f|--format] [--fallback-extensions] [--files-from] [--generate] [--github-token] [--glob-ignore-case] [-h|--help] [-H|--header] [--hidden] [--host-concurrency] [--host-request-interval] [--host-stats] [-i|--insecure] [--include] [--include-fragments] [--include-mail] [--include-verbatim] [--include-wikilinks] [--index-files] [-m|--max-redirects] [--max-cache-age] [--max-concurrency] [--max-retries] [--min-tls] [--mode] [-n|--no-progress] [--no-ignore] [-o|--output] [--offline] [-p|--preprocess] [-q|--quiet]... [-r|--retry-wait-time] [--remap] [--require-https] [--root-dir] [-s|--scheme] [--skip-missing] [--suggest] [-t|--timeout] [-T|--threads] [-u|--user-agent] [-v|--verbose]... [-V|--version] [-X|--method] [inputs]

lychee is a fast, asynchronous link checker which detects broken URLs and mail addresses in local files and websites. It supports Markdown and HTML and works with other file formats.

lychee is powered by lychee-lib, the Rust library for link checking.

A List of accepted status codes for valid links

The following accept range syntax is supported: [start]..[[=]end]|code. Some valid examples are:

- 200 (accepts the 200 status code only) - ..204 (accepts any status code < 204) - ..=204 (accepts any status code <= 204) - 200..=204 (accepts any status code from 200 to 204 inclusive) - 200..205 (accepts any status code from 200 to 205 excluding 205, same as 200..=204)

Use "lychee --accept '200..=204, 429, 500' <inputs>..." to provide a comma- separated list of accepted status codes. This example will accept 200, 201, 202, 203, 204, 429, and 500 as valid status codes.

[default: 100..=103,200..=299]

Accept timed out requests and return exit code 0 when encountering timeouts but not any other errors
Web archive to use to provide suggestions for `--suggest`.

[default: wayback]

Possible values:

•
wayback
Base URL to use when resolving relative URLs in local files. If specified, relative links in local files are interpreted as being relative to the given base URL.

For example, given a base URL of `https://example.com/dir/page`, the link `a` would resolve to `https://example.com/dir/a` and the link `/b` would resolve to `https://example.com/b`. This behavior is not affected by the filesystem path of the file containing these links.

Note that relative URLs without a leading slash become siblings of the base URL. If, instead, the base URL ended in a slash, the link would become a child of the base URL. For example, a base URL of `https://example.com/dir/page/` and a link of `a` would resolve to `https://example.com/dir/page/a`.

Basically, the base URL option resolves links as if the local files were hosted at the given base URL address.

The provided base URL value must either be a URL (with scheme) or an absolute path. Note that certain URL schemes cannot be used as a base, e.g., `data` and `mailto`.

Deprecated; use `--base-url` instead
Basic authentication support. E.g. `http://example.com username:password`
Configuration file to use. Can be specified multiple times.

If given multiple times, the configs are merged and later occurrences take precedence over previous occurrences.

[default: lychee.toml]

Use request cache stored on disk at `.lycheecache`
A list of status codes that will be ignored from the cache

The following exclude range syntax is supported: [start]..[[=]end]|code. Some valid examples are:

- 429 (excludes the 429 status code only) - 500.. (excludes any status code >= 500) - ..100 (excludes any status code < 100) - 500..=599 (excludes any status code from 500 to 599 inclusive) - 500..600 (excludes any status code from 500 to 600 excluding 600, same as 500..=599)

Use "lychee --cache-exclude-status '429, 500..502' <inputs>..." to provide a comma-separated list of excluded status codes. This example will not cache results with a status code of 429, 500 and 501.

Read and write cookies using the given file. Cookies will be stored in the cookie jar and sent with requests. New cookies will be stored in the cookie jar and existing cookies will be updated.
This is the default file extension that is applied to files without an extension.

This is useful for files without extensions or with unknown extensions. The extension will be used to determine the file type for processing.

Examples:
--default-extension md
--default-extension html

Don't perform any link checking. Instead, dump all the links extracted from inputs that would be checked
Don't perform any link extraction and checking. Instead, dump all input sources from which links would be collected
Exclude all private IPs from checking. Equivalent to `--exclude-private --exclude-link-local --exclude-loopback`
Exclude URLs and mail addresses from checking. The values are treated as regular expressions
Deprecated; use `--exclude-path` instead
Exclude link-local IP address range from checking
Exclude loopback IP address range and localhost from checking
Exclude paths from getting checked. The values are treated as regular expressions
Exclude private IP address ranges from checking
A list of file extensions. Files not matching the specified extensions are skipped.

Multiple extensions can be separated by commas. Note that if you want to check filetypes, which have multiple extensions, e.g. HTML files with both .html and .htm extensions, you need to specify both extensions explicitly. An example is: `--extensions html,htm,php,asp,aspx,jsp,cgi`.

This is useful when the default extensions are not enough and you don't want to provide a long list of inputs (e.g. file1.html, file2.md, etc.)

[default: md,mkd,mdx,mdown,mdwn,mkdn,mkdown,markdown,html,htm,css,txt,xml]

Output format of final status report

[default: compact]

Possible values:

  • compact
  • detailed
  • json
  • junit
  • markdown
When checking locally, attempts to locate missing files by trying the given fallback extensions. Multiple extensions can be separated by commas. Extensions will be checked in order of appearance.

Example: --fallback-extensions html,htm,php,asp,aspx,jsp,cgi

Note: This option takes effect on `file://` URIs which do not exist and on
`file://` URIs pointing to directories which resolve to themself (by the
--index-files logic).

Read input filenames from the given file or stdin (if path is '-').

This is useful when you have a large number of inputs that would be cumbersome to specify on the command line directly.

Examples:


lychee --files-from list.txt
find . -name '*.md' | lychee --files-from -
echo 'README.md' | lychee --files-from -

File Format: - Each line should contain one input (file path, URL, or glob pattern). - Lines starting with '#' are treated as comments and ignored. - Empty lines are also ignored.

Generate special output (e.g. the man page) instead of performing link checking

Possible values:

  • man
  • complete-bash
  • complete-elvish
  • complete-fish
  • complete-powershell
  • complete-zsh
GitHub API token to use when checking github.com links, to avoid rate limiting
Ignore case when expanding filesystem path glob inputs
Print help (see a summary with '-h')
Set custom header for requests.

Some websites require custom headers to be passed in order to return valid responses. You can specify custom headers in the format 'Name: Value'. For example, 'Accept: text/html'. This is the same format that other tools like curl or wget use. Multiple headers can be specified by using the flag multiple times. The specified headers are used for ALL requests. Use the `hosts` option to configure headers on a per-host basis.

Do not skip hidden directories and files
Default maximum concurrent requests per host (default: 10)

This limits the maximum amount of requests that are sent simultaneously to the same host. This helps to prevent overwhelming servers and running into rate-limits. Use the `hosts` option to configure this on a per-host basis.

Examples:
--host-concurrency 2 # Conservative for slow APIs
--host-concurrency 20 # Aggressive for fast APIs

Minimum interval between requests to the same host (default: 50ms)

Sets a baseline delay between consecutive requests to prevent overloading servers. The adaptive algorithm may increase this based on server responses (rate limits, errors). Use the `hosts` option to configure this on a per-host basis.

Examples:
--host-request-interval 50ms # Fast for robust APIs
--host-request-interval 1s # Conservative for rate-limited APIs

Show per-host statistics at the end of the run
Proceed for server connections considered insecure (invalid TLS)
URLs to check (supports regex). Has preference over all excludes
Enable the checking of fragments in links.

Use `none` to disable fragment checks, `anchor-only` for anchor fragments like `#section`, `text-only` for text fragments like `#:~:text=example`, or `full` to check both.

If provided without a value, defaults to `anchor-only`.

Also check email addresses
Find links in verbatim sections like `pre`- and `code` blocks
Check WikiLinks in Markdown files, this requires specifying --base-url
When checking locally, resolves directory links to a separate index file. The argument is a comma-separated list of index file names to search for. Index names are relative to the link's directory and attempted in the order given.

If `--index-files` is specified, then at least one index file must exist in order for a directory link to be considered valid. Additionally, the special name `.` can be used in the list to refer to the directory itself.

If unspecified (the default behavior), index files are disabled and directory links are considered valid as long as the directory exists on disk.

Example 1: `--index-files index.html,readme.md` looks for index.html or readme.md
and requires that at least one exists.

Example 2: `--index-files index.html,.` will use index.html if it exists, but
still accept the directory link regardless.

Example 3: `--index-files ''` will reject all directory links because there are
no valid index files. This will require every link to explicitly name
a file.

Note: This option only takes effect on `file://` URIs which exist and point to a directory.

Maximum number of allowed redirects

[default: 10]

Discard all cached requests older than this duration

[default: 1d]

Maximum number of concurrent network requests

[default: 128]

Maximum number of retries per request

[default: 3]

Minimum accepted TLS Version

Possible values:

  • TLSv1_0
  • TLSv1_1
  • TLSv1_2
  • TLSv1_3
Set the output display mode. Determines how results are presented in the terminal

[default: color]

Possible values:

  • plain
  • color
  • emoji
  • task
Do not show progress bar. This is recommended for non-interactive shells (e.g. for continuous integration)
Do not skip files that would otherwise be ignored by '.gitignore', '.ignore', or the global ignore file
Output file of status report
Only check local files and block network requests
Preprocess input files with the given command.

For each file input, this flag causes lychee to execute `COMMAND PATH` and process its standard output instead of the original contents of PATH. This allows you to convert files that would otherwise not be understood by lychee. The preprocessor COMMAND is only run on input files, not on standard input or URLs.

To invoke programs with custom arguments or to use multiple preprocessors, use a wrapper program such as a shell script. An example script looks like this:

``` #!/usr/bin/env bash case "$1" in *.pdf)
exec pdftohtml -i -s -stdout "$1"
;; *.odt|*.docx|*.epub|*.ipynb)
exec pandoc "$1" --to=html --wrap=none
;; *)
# identity function, output input without changes
exec cat
;; esac ```

Less output per occurrence (e.g. `-q` or `-qq`)
Minimum wait time in seconds between retries of failed requests

[default: 1]

Remap URI matching pattern to different URI
When HTTPS is available, treat HTTP links as errors
Root directory to use when checking absolute links in local files. This option is required if absolute links appear in local files, otherwise those links will be flagged as errors. This must be an absolute path (i.e., one beginning with `/`).

If specified, absolute links in local files are resolved by prefixing the given root directory to the requested absolute link. For example, with a root-dir of `/root/dir`, a link to `/page.html` would be resolved to `/root/dir/page.html`.

This option can be specified alongside `--base-url`. If both are given, an absolute link is resolved by constructing a URL from three parts: the domain name specified in `--base-url`, followed by the `--root-dir` directory path, followed by the absolute link's own path.

Only test links with the given schemes (e.g. https). Omit to check links with any other scheme. At the moment, we support http, https, file, and mailto.
Skip missing input files (default is to error if they don't exist)
Suggest link replacements for broken links, using a web archive. The web archive can be specified with `--archive`
Website timeout in seconds from connect to response finished

[default: 20]

Number of threads to utilize. Defaults to number of cores available to the system
User agent

[default: lychee/x.y.z]

Set verbosity level; more output per occurrence (e.g. `-v` or `-vv`)
Print version
Request method

[default: get]

[inputs]
Inputs for link checking (where to get links to check from). These can be: files (e.g. `README.md`), file globs (e.g. `'~/git/*/README.md'`), remote URLs (e.g. `https://example.com/README.md`), or standard input (`-`). Alternatively, use `--files-from` to read inputs from a file.

NOTE: Use `--` to separate inputs from options that allow multiple arguments.

Check all links in supported files by specifying a directory


$ lychee .

Specify files explicitly or use glob patterns


$ lychee README.md test.html info.txt
$ lychee 'public/**/*.html' '*.md'

Check all links on a website


$ lychee https://example.com

Check links from stdin


$ cat test.md | lychee -
$ echo 'https://example.com' | lychee -

Links can be excluded and included with regular expressions


$ lychee --exclude '^https?://blog\.example\.com' --exclude '\.(pdf|zip|png|jpg)$' .

Further examples can be found in the online documentation at https://lychee.cli.rs

0 Success. The operation was completed successfully as instructed.

1 Missing inputs or any unexpected runtime failures or configuration errors

2 Link check failures. At least one non-excluded link failed the check.

3 Encountered errors in the config file.

Report any bugs or questions to https://github.com/lycheeverse/lychee/issues/

Questions can also be asked on https://github.com/lycheeverse/lychee/discussions

v0.24.2

Matthias Endler <matthias@endler.dev>

Thomas Zahner <thomas.zahner@protonmail.ch>

A huge thank you to all the wonderful contributors who helped make this project a success.

2026-05-01 lychee 0.24.2