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Markdown Viewer / Chrome Extension

Available at Chrome Store

Features

Table of Contents

After Install

Local Files

  1. Navigate to chrome://extensions
  2. Make sure that the Allow access to file URLs checkbox is checked for the Markdown Viewer extension

file-urls

Remote Files

  1. Click on the Markdown Viewer icon and select Advanced Options
  2. Add the origins that you want enabled for the Markdown Viewer extension

Compiler Options

Marked

Option Default Description
breaks false Enable GFM line breaks. This option requires the gfm option to be true.
gfm true Enable GFM GitHub Flavored Markdown.
pedantic false Conform to obscure parts of markdown.pl as much as possible. Don't fix any of the original markdown bugs or poor behavior.
sanitize false Sanitize the output. Ignore any HTML that has been input.
smartLists false Use smarter list behavior than the original markdown. May eventually be default with the old behavior moved into pedantic.
smartypants false Use "smart" typographic punctuation for things like quotes and dashes.
tables true Enable GFM tables. This option requires the gfm option to be true.

Remark

Option Default Description
breaks false Enable GFM line breaks. This option requires the gfm option to be true.
commonmark false Toggle CommonMark mode.
footnotes false Toggle reference footnotes and inline footnotes.
gfm true Enable GFM GitHub Flavored Markdown.
pedantic false Conform to obscure parts of markdown.pl as much as possible. Don't fix any of the original markdown bugs or poor behavior.
sanitize false Sanitize the output. Ignore any HTML that has been input.

Content Options

Option Default Description
emoji false Convert emoji :shortnames: into EmojiOne images
scroll true Remember scroll position
toc false Generate Table of Contents
mathjax false Render TeX and LaTeX math blocks

Scroll

  • Enable the scroll option while you are working on a markdown document and you are frequently refreshing the page. Also useful when you are reading long document and you want to continue from where you left off.
  • Disable the scroll option if you want the page rendered at the top or scrolled down to a certain header if a hash URL fragment is present.

TOC

  • Generates Table of Contents (TOC) based on the headers found in the markdown document.

MathJax

The following mathjax delimiters are supported:

  • inline math: \(math\) and $math$
  • display math: \[math\] and $$math$$

The following rules apply to your content when mathjax is enabled:

  • Regular dollar sign $ in text that is not part of a math formula should be escaped: \$
  • Regular markdown escaping for parentheses: \( and \), and brackets: \[ and \] is not supported. MathJax will convert anything between these delimiters to math formulas, unless they are wrapped in backticks: `\(` or fenced code blocks.

Emoji

  • Emoji shortnames like: :sparkles: will be converted to ✨ using EmojiOne images.
  • Currently unicode symbols like ✨ and ASCII emoji like :D are not supported.

Advanced Options

Detecting and rendering local file URLs can be enabled easily using the Allow access to file URLs option for the extension.

Access to remote URLs however, should be enabled manually.

Add Origin

Here is how you can enable the extension for the https://raw.githubusercontent.com origin:

add-origin

The origin consists of protocol part and domain part. The protocol can be either https, http, or a * to match both https and http.

Enable the above origin and play around with the extension here.

Note that the remote origins should either provide a valid HTTP header (see Header Detection) and/or valid URL path (see Path Matching). Otherwise you'll have to add the origin explicitly and modify its Path Matching regular expression.

Add All Origins

In case you really want to you can enable the extension for all origins:

all-origins

Alternatively you can use the Allow All button.

Header Detection

When this option is enabled the extension will check for the text/markdown and text/x-markdown content-type header before trying to match the path:

header-detection

Path Matching

If the header detection is disabled or a proper content-type header is missing, the extension will check if the URL is ending with a markdown file extension:

path-regexp

It's a simple regular expression that matches URLs ending with:

  • markdown file extension: \.(?:markdown|mdown|mkdn|md|mkd|mdwn|mdtxt|mdtext|text)
  • and optionally anchor or querystring after that: (?:#.*|\?.*)?

The ?: used in (?:match) stands for non-capturing group and it's there for performance reasons.

You can modify the path matching regular expression for each enabled origin individually. The settings are being updated as you type.

Remove Origin

At any point click on the small x button next to the origin that you want to remove. This actually removes the permission itself so that the extension is no longer able to inject scripts into that origin.

Note that the Chrome's consent popup shows up only when you add the origin for the first time. In case you re-add it you'll no longer see that popup. That's a Chrome thing and it's not controllable through the extension.

Refresh Origin

The extension synchronizes your preferences across all your devices using Google Sync. The list of your allowed origins is being synced too, but the actual permissions that you give using the Chrome's consent popup cannot be synced.

In case you recently added a new origin on one of your devices you'll have to explicitly allow it on your other devices. The little refresh button next to each origin is used for that.

Markdown Syntax and Features

A few files located in the test folder of this repo can be used to test what's possible with Markdown Viewer:

  • Add the raw.githubusercontent.com origin through the Advanced Options
  • Navigate to the test files: syntax, mathjax, yaml, toml and play around with the Compiler and Content options
  • Use the Markdown/HTML button to switch between raw markdown and rendered HTML
  • At any point click on the Defaults button to reset back the compiler options

More Compilers

Markdown Viewer can be used with any markdown parser/compiler. Currently the following compilers are implemented: marked, remark, showdown, markdown-it, remarkable, commonmark, markdown-js.

  1. Clone the compilers branch
  2. Navigate to chrome://extensions
  3. Make sure that the Developer mode checkbox is checked at the top
  4. Disable the Markdown Viewer extension downloaded from the Chrome Store
  5. Click on the Load unpacked extension... button and select the cloned directory

License

The MIT License (MIT)

Copyright (c) 2013-2017 Simeon Velichkov [email protected]

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.