Text Tools
Markdown Linter
Lint Markdown against markdownlint MD001 to MD047 rules in your browser. See errors with line numbers, hints, and one-click safe auto-fix.
Samples
Lint results
- warningMD022line 1, col 1
Heading is not followed by a blank line.
Add a blank line below the heading.
#Welcome to the Project
- errorMD018line 1, col 2auto-fix
Missing space after #.
Put exactly one space between # and the heading text.
#Welcome to the Project
- warningMD012line 4, col 1auto-fix
More than one consecutive blank line.
Collapse runs of blank lines into a single blank line.
- warningMD012line 5, col 1auto-fix
More than one consecutive blank line.
Collapse runs of blank lines into a single blank line.
- warningMD022line 6, col 1
Heading is not followed by a blank line.
Add a blank line below the heading.
## Setup
- warningMD019line 6, col 3auto-fix
Heading has 2 spaces after #.
Use exactly one space between # and the heading text.
## Setup
- warningMD029line 7, col 1
Ordered list prefix is not consistent.
Either start every item with 1. (lazy) or count up 1., 2., 3., ...
1. Clone the repo
- warningMD032line 7, col 1
List is not preceded by a blank line.
Add a blank line above the list.
1. Clone the repo
- warningMD029line 8, col 1
Ordered list prefix is not consistent.
Either start every item with 1. (lazy) or count up 1., 2., 3., ...
1. Install deps
- warningMD029line 9, col 1
Ordered list prefix is not consistent.
Either start every item with 1. (lazy) or count up 1., 2., 3., ...
2. Run
- errorMD001line 11, col 1
Heading skipped from H2 to H4.
Use H3 so heading levels increment by one.
#### Skipped heading
- warningMD032line 11, col 1
List is not followed by a blank line.
Add a blank line below the list.
#### Skipped heading
- warningMD019line 11, col 5auto-fix
Heading has 2 spaces after #.
Use exactly one space between # and the heading text.
#### Skipped heading
- errorMD011line 13, col 17
Reversed link syntax detected.
Use [text](url): square brackets for the text, parentheses for the URL.
Here is a link: (Docs)[https://example.com] and a bare URL https://example.com/path.
- warningMD034line 13, col 24
Bare URL in text.
Wrap the URL in <angle brackets> or as [text](url).
Here is a link: (Docs)[https://example.com] and a bare URL https://example.com/path.
- warningMD034line 13, col 60
Bare URL in text.
Wrap the URL in <angle brackets> or as [text](url).
Here is a link: (Docs)[https://example.com] and a bare URL https://example.com/path.
- warningMD030line 18, col 2auto-fix
Use exactly one space after "*".
Trim the extra spaces after the bullet.
* Bullet two
- warningMD032line 23, col 1
List is not followed by a blank line.
Add a blank line below the list.
Body text right after.
- errorMD042line 25, col 1
Link has empty URL.
Provide a URL between the parentheses.
[click here]()
- errorMD042line 26, col 1
Link has empty text.
Provide visible link text between the square brackets.
[](https://example.com)
- warningMD047line 28, col 60auto-fix
File does not end with a newline.
Add a single trailing newline.
Some inline HTML <span class="bold">looks like this</span>.
Rules
Toggle individual rules. Switching from a preset moves you to Custom.
How to use
- Paste your Markdown into the input on the left, or pick a sample (Messy README, Clean post, Trailing spaces, Skipped headings) to load one.
- Pick a preset: Recommended (sensible defaults), Strict (every rule on), or Custom (toggle rules individually).
- Read the results on the right. Use the Errors and Warnings tabs to focus on the most important issues.
- Click Auto-fix safe issues to apply the unambiguous fixes (trailing spaces, hard tabs, blank-line collapse, heading and list spacing, final newline).
- Fix the remaining structural issues by hand and re-lint. Use Copy report to paste the findings into a PR comment.
About this tool
Markdown Linter checks any Markdown document against the practical subset of markdownlint rules that catch the real bugs in README files, blog posts, and documentation sites. Paste your Markdown and the tool walks the source and reports every violation with the same MD-prefix codes (MD001, MD009, MD013, MD025, MD040, and many more) that the npm markdownlint tool uses, so the findings carry straight into a CI config. The Recommended preset matches the project defaults that most repos run (line length and inline HTML are off so prose stays unblocked), the Strict preset enables every rule, and Custom lets you toggle each rule individually. Implemented rules include MD001 (heading levels increment by one), MD003 (consistent heading style), MD009 (no trailing spaces, with the two-space hard break exception), MD010 (no hard tabs outside fenced code), MD011 (reversed link syntax), MD012 (no consecutive blank lines), MD013 (line length with a configurable limit), MD018 and MD019 (single space after ATX hashes), MD022 (blank lines around headings), MD023 (heading starts at column 1), MD025 (single H1), MD026 (no trailing punctuation in headings), MD027 (one space after blockquote marker), MD029 (ordered list prefix style), MD030 (spaces after list markers), MD031 (blank lines around fenced code), MD032 (blank lines around lists), MD033 (inline HTML), MD034 (bare URLs), MD038 (no padding inside code spans), MD040 (language tag on fenced code blocks), MD042 (no empty links), and MD047 (single trailing newline). Each issue carries the rule code, severity, line, column, message, a hint on how to fix it, and the original line snippet so the bad character is one Ctrl+F away. A copy-ready report button captures every issue for pasting into a PR comment or a doc review. The Auto-fix safe issues button applies a careful pass for the rules whose fix is unambiguous (trailing spaces, hard tabs, blank-line collapse, ATX heading spacing, leading whitespace on headings, blockquote and list marker spacing, and the final newline) so the obvious mess goes away in one click and you can focus on the structural issues that need human judgment. Useful for tidying up an inherited README before a release, enforcing a style guide on a docs site, debugging a Markdown file that renders oddly in GitHub or MkDocs, or pre-checking content before pasting into a CMS that runs its own Markdown processor. Everything runs locally in your browser. The Markdown you paste never leaves your device.
Free to use. Works in your browser. No signup, no login.
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