linkcheck
Very fast link-checking.
Philosophy:
A good utility is custom-made for a job. There are many link checkers out there, but none of them seems to be striving for the following set of goals.
Crawls fast
-
You want to run the link-checker at least before every deploy (on CI or manually). When it takes ages, you're less likely to do so.
-
linkcheck
is currently several times faster than blc and all other link checkers that go to at least comparable depth. It is 40 times faster than the only tool that goes to the same depth (linkchecker).
Finds all relevant problems
-
No link-checker can guarantee correct results: the web is too flaky for that. But at least the tool should correctly parse the HTML (not just try to guess what's a URL and what isn't) and the CSS (for
url(...)
links).- PENDING: srcset support
-
linkcheck
finds more than linklint and blc. It finds the same amount or more problems than the best alternative, linkchecker.
Leaves out irrelevant problems
-
linkcheck
doesn't attempt to render JavaScript. It would make it at least an order of magnitude slower and way more complex. (For example, what links and buttons should the tool attempt to click, and how many times? Should we only click visible links? How exactly do we detect broken links?) Validating SPAs is a very different problem than checking static links, and should be approached by dedicated tools. -
linkcheck
only supportshttp:
andhttps:
. It won't try to check FTP or telnet or nntp links.- Note:
linkcheck
will currently completely ignore unsupported schemes likeftp:
ormailto:
ordata:
. This may change in the future to at least show info-level warning.
- Note:
-
linkcheck
doesn't validate file system directories. Servers often behave very differently than file systems, so validating links on the file system often leads to both false positives and false negatives. Links should be checked in their natural habitat, and as close to the production environment as possible. You can (and should) runlinkcheck
on your localhost server, of course.
Good UX
-
Yes, a command line utility can have good or bad UX. It has mostly to do with giving sane defaults, not forcing users to learn new constructs, not making them type more than needed, and showing concise output.
-
The most frequent use cases should be only a few arguments.
- For example, unleashing
linkcheck
on http://localhost:4001/ can be done vialinkcheck :4001
.
- For example, unleashing
-
linkcheck
doesn't throttle itself on localhost. -
linkcheck
follows POSIX CLI standards (no@input
and similar constructs like in linklint).
Brief and meaningful output
-
When everything works, you don't want to see a huge list of links.
- In this scenario,
linkcheck
just outputs 'Perfect' and some stats on a single line.
- In this scenario,
-
When things are broken, you want to see where exactly is the problem and you want to have it sorted in a sane way.
linkcheck
lists broken links by their source URL first so that you can fix many links at once. It also sorts the URLs alphabetically, and shows both the exact location of the link (line:column) and the anchor text (or the tag if it wasn't an anchor).
-
For CI builds, you want non-zero exit code whenever there is a problem.
linkcheck
returns status code1
if there are warnings, and status code2
if there are errors.
It goes without saying that linkcheck
honors robots.txt and throttles itself
when accessing websites.
Installation
Direct download
- Download the latest executable from the
Releases page on GitHub.
Pick the executable for your system (for example,
linkcheck-win-x64.exe
for a 64-bit machine running Microsoft Windows).
You should be able to immediately run this executable -- it has no external
dependencies. For example, assuming you are on MacOS and downloaded the file
to the default downloads directory, you can go to your Terminal
(or iTerm, or SSH) and run ./Downloads/linkcheck-mac-x64
.
You can rename the file and move it to any directory. For example,
on a Linux box, you might want to rename the executable to simply
linkcheck
, and move it to /usr/local/bin
, $HOME/bin
or another
directory in your $PATH
.
From Source
Step 1. Install Dart
Full installation guides per platform:
For example, on a Mac, assuming you have homebrew, you just run:
$ brew tap dart-lang/dart
$ brew install dart
linkcheck
Step 2. Install Once Dart is installed, run:
$ pub global activate linkcheck
Pub installs executables into ~/.pub-cache/bin
, which may not be on your path.
You can fix that by adding the following to your shell's config file (.bashrc,
.bash_profile, etc.):
export PATH="$PATH":"~/.pub-cache/bin"
Then either restart the terminal or run source ~/.bash_profile
(assuming
~/.bash_profile
is where you put the PATH export above).
Docker
If you have Docker installed, you can build the image and use the container avoiding local Dart installation.
Build
In the project directory, run
docker build -t filiph/linkcheck .
Usage (container mode)
docker run filiph/linkcheck <URL>
All bellow usage are valid running on container too.
Usage
If in doubt, run linkcheck -h
. Here are some examples to get you started.
Localhost
Running linkcheck
without arguments will try to crawl
http://localhost:8080/ (which is the most common local server URL).
linkcheck
to crawl the site and ignore external linkslinkcheck -e
to try external links
If you run your local server on http://localhost:4000/, for example, you can do:
linkcheck :4000
to crawl the site and ignore external linkslinkcheck :4000 -e
to try external links
linkcheck
will not throttle itself when accessing localhost. It will go as
fast as possible.
Deployed sites
linkcheck www.example.com
to crawl www.example.com and ignore external linkslinkcheck https://www.example.com
to start directly on httpslinkcheck www.example.com www.other.com
to crawl both sites and check links between the two (but ignore external links outside those two sites)
Many entry points
Assuming you have a text file mysites.txt
like this:
http://egamebook.com/
http://filiph.net/
https://alojz.cz/
You can run linkcheck -i mysites.txt
and it will crawl all of them and also
check links between them. This is useful for:
- Link-checking projects spanning many domains (or subdomains).
- Checking all your public websites / blogs / etc.
There's another use for this, and that is when you have a list of inbound links, like this:
http://www.dartlang.org/
http://www.dartlang.org/tools/
http://www.dartlang.org/downloads/
You probably want to make sure you never break your inbound links. For example, if a page changes URL, the previous URL should still work (redirecting to the new page when appropriate).
Where do you get a list of inbound links? Try your site's sitemap.xml as a starting point, and — additionally — try something like the Google Webmaster Tools’ crawl error page.
Skipping URLs
Sometimes, it is legitimate to ignore some failing URLs. This is done via
the --skip-file
option.
Let's say you're working on a site and a significant portion of it is currently
under construction. You can create a file called my_skip_file.txt
, for
example, and fill it with regular expressions like so:
# Lines starting with a hash are comments.
admin/
\.s?css$
\#info
The file above includes a comment on line 1 which will be ignored. Line 2 is
blank and will be ignored as well. Line 3 contains a broad regular expression
that will make linkcheck ignore any link to a URL containing admin/
anywhere in it. Line 4 shows that there is full support for
regular expressions – it will ignore URLs ending with .css
and
.scss
. Line 5 shows the only special escape sequence.
If you need to start your regular expression with a #
(which linkcheck would normally parse as a comment) you can
precede the #
with a backslash (\
). This will force linkcheck
not to ignore the line. In this case, the regular expression on line 4
will match #info
anywhere in the URL.
To use this file, you run linkcheck like this:
linkcheck example.com --skip-file my_skip_file.txt
Regular expressions are hard. If unsure, use the -d
option to see what URLs
your skip file is ignoring, exactly.
To use a skipfile while running linkchecker through docker create a directory to use as a volume in docker and put your skip file in it. Then use a command simliar to the following (assuming the folder was named skipfiles):
docker run -v "$(pwd)/skipfiles/:/skipfiles/" filiph/linkcheck http://example.com/ --skip-file /skipfiles/skipfile.txt
User agent
The tool identifies itself to servers with the following user agent string:
linkcheck tool (https://github.com/filiph/linkcheck)