How to Preview Markdown Online and Check the Result

An online Markdown viewer turns a plain-text document into headings, paragraphs, lists, and other formatted content. Use it to read a .md attachment or review a draft before publishing. The useful question is whether the viewer supports the syntax and output your document needs.

This guide describes the current MD File Viewer workflow and the checks to make before trusting a preview.

Open a file or paste a draft

1. Open the Markdown viewer for a rendered view, or the MD opener to select a local file.
2. Paste text or choose a .md, .markdown, or .txt file. The file is read in your browser.
3. Compare the source and preview. On a narrow screen, use the preview control when the editor and result do not fit side by side.
4. Keep your original .md file. A preview or exported document is a separate representation of that source.

Use this small test before importing a longer document:

# Review checklist

- [x] Import the source
- [ ] Check the destination

| Format | Purpose |
| --- | --- |
| Markdown | Edit the source |
| HTML | Publish on the web |

> Preview before sharing.

You should see a heading, two task items, a two-column table, and a quote. If the table stays as pipe characters, check that the separator row is present. If a whole section looks like code, look for an unclosed code fence.

A preview is specific to its renderer

CommonMark defines core Markdown. GitHub Flavored Markdown adds extensions such as tables and task lists. GitHub also applies its own styles, HTML sanitization, and platform features. A GFM-capable viewer cannot promise an identical GitHub page.

The viewer supports common headings, lists, links, code, GFM tables and task lists. Mermaid diagrams and math are additional features. Raw HTML from user input is removed, so <u>, <ins>, and <br> do not behave as they do in every HTML-enabled editor. Use Markdown emphasis and explicit Markdown line breaks where possible.

If your destination is a README, wiki, or publishing platform, check its final preview too. Heading anchors, relative links, alerts, fonts, and diagrams can differ. A local link such as ./images/chart.png also needs its surrounding files; importing only a .md file does not import an entire project directory.

Browser processing and privacy

The Markdown parsing and the file-reading operation run in the browser; the tool does not upload the document to a conversion endpoint. That describes document processing, not every network request made by a web page.

An image such as ![chart](https://example.com/chart.png) can cause the browser to contact the image host. Following links also contacts their destination. Loading the site and optional analytics or advertising services involves separate network activity; see the privacy policy.

The homepage editor saves a draft in this browser's local storage so it can restore your work. Local storage is not a backup or encryption system, and another person using the same browser profile may access that draft. Follow your organization's rules for confidential documents, and use a local editor when those rules require one. Initial page loads, lazy-loaded libraries, and remote images may need a network connection; offline operation is not guaranteed.

Choose an output for the recipient

Output	Use it for	Check before sending
HTML	Web content and CMS input	Styles, relative URLs, math stylesheet, destination sanitization
Word	Editable text and review	Lists, tables, image loading; Mermaid remains code; math is unsupported and may be omitted
PDF	A visual document with fixed pages	Current download is image based; text and links are not interactive
Image	A short visual card	Cropping, resolution, image permissions, and a text alternative

For a PDF with selectable text, use the browser's print dialog on a suitable rendered page and inspect the saved result. A screenshot-style PDF is useful for appearance, but does not provide a tagged, accessible document or a navigable text outline.

Before sharing

Read the rendered result from top to bottom. Test a representative table, a nested list, each diagram, and the longest code block. Open the actual exported file too: a correct web preview does not prove that another format preserved every feature.

For syntax fixes, use the cheat sheet. For compatibility details, the underline guide and horizontal line guide explain two common sources of confusion.