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 trust rail: 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.
Why does the trust rail mention a file host?
marked and highlight.js may load from jsDelivr or cdnjs. That is library bytes. 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.