README preview without opening an Electron app
Use this when you are drafting a README, a GitHub issue, or a note with tables and fenced code, and you want to see the HTML before you commit. Flavor is GitHub-flavored Markdown via marked: tables, task lists, strikethrough, autolinks. highlight.js colors fenced blocks. I would rather you keep the Markdown in git and treat copied HTML as an export, not as the source of truth.
The honest exception is already on the privacy panel: marked and highlight.js may load from an outside file host (jsDelivr / cdnjs). That hop is library bytes, not your document. Watch the compute log. Your textarea is not posted to Privy Tools. If that distinction feels too fine, draft in a local editor. This page exists for the 20-minute README, not for a novel you do not want on a CDN request log next to a script fetch.
Worked example: a four-column table
Pipe table, header row, separator, three body rows. GFM alignment with colons on the separator is supported. If a cell contains a raw pipe, escape it or the column count breaks and the preview looks like one smashed row. Word count on a typical “Feature / Supported / Notes” table with 12 rows sits around 80–120 words; the HTML will be larger because of <td> noise. If GitHub’s preview and this one disagree on a table, GitHub wins for a README that will be read on GitHub.
Worked example: a 12-line JavaScript fence
A fenced block marked javascript, 12 lines, ~280 characters of code. highlight.js will color it after the library loads. If the language tag is a typo (javscript), you get autodetect or a plain <pre>. That is a preview issue, not a git issue. Copying the highlighted HTML into a CMS can drag highlight.js classes with it. Prefer copying Markdown. The word/character/line counters on this page count the source, including the fence ticks and the language tag.
Worked example: a gist that still has a script tag
People paste READMEs from strangers. marked can pass raw HTML through. I strip script, iframe, object, embed, link, meta, and base before the preview is inserted. That is a seatbelt for this tab, not a sanitizer you should copy into a public comment system. An <img onerror=…> is a different class of problem. If you are previewing untrusted Markdown, assume the preview is for your eyes, then throw the HTML away. marked is configured with breaks: true, so a single newline in a paragraph becomes a line break here; CommonMark would keep that as a space. If a README looks “too stacked” compared to GitHub, that flag is why.
What this will not render
Mermaid diagrams are not bundled. MathJax is not bundled. GitHub-only alerts and footnote quirks may not match. Print-to-PDF via the browser is a print stylesheet, not a typesetting engine. Task-list checkboxes in the preview are not a project manager. A 40,000-word draft will live-preview slowly; this is a README glass, not a novel IDE. If you need the HTML in production, run a sanitizer you chose, not this page’s preview helper.
Questions
Which flavor is this?
GitHub-flavored Markdown via marked: tables, task lists, strikethrough. If GitHub’s README preview disagrees, GitHub wins for a file that will be read there.
Where do marked and highlight.js come from?
Pinned files on this origin (marked 11.0.0, highlight.js 11.9.0). The Markdown in the textarea is not posted to Privy Tools.
Can I paste a stranger’s README?
For your own eyes, yes. I strip script/iframe and friends in the preview. Do not copy that HTML into a public CMS and call it sanitized.
Where did my Mermaid chart go?
Not bundled. Keep the fence in git and render it on GitHub, or use a dedicated diagram tool.
Should I commit the HTML?
Usually no. Commit Markdown. Copy HTML only when a CMS has no Markdown field.
How do I get a PDF?
Browser print dialog. It is a print of the preview, not a typeset manual.