Browser text tools
Markdown, HTML, and active-content boundaries in a browser tool
Formatting Markdown or HTML can improve readability, but a browser preview is not a license to run unknown scripts, trust embedded content, or treat a rendered document as a security review.
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Text formatting and code execution are different operations
Markdown is a lightweight text convention. HTML can describe document structure, links, images, forms, and more. Some HTML features can also load external resources or execute behaviour in certain contexts. A safe formatter should be clear about what it renders, escapes, blocks, or leaves as text.
Do not paste passwords, private tokens, contracts, medical information, source code under confidentiality, or other sensitive data into any tool until you understand its privacy boundary. Local browser processing reduces a server-transfer step; it does not make the content risk-free in every environment.
Worked example: a Markdown preview with a suspicious link
A Markdown note can contain a link whose visible label says “Read the report” while its destination points somewhere unexpected. A formatter can make the note easier to scan, but it cannot decide whether the link is trustworthy. Inspect the actual URL before following it.
Likewise, a pasted HTML fragment might include scripts, external images, forms, or event handlers. Treat unknown active content as a review problem, not as ordinary prose. A rendered appearance is not proof of benign behaviour.
| Input feature | A formatter can help with | It cannot establish |
|---|---|---|
| Markdown headings and lists | Readable structure and consistent text. | Truth, ownership, or safety of the content. |
| A visible URL | Showing the link text and destination. | That a destination is safe or appropriate. |
| HTML markup | Escaping, displaying, or selectively previewing it. | That scripts, embeds, or network activity are harmless. |
Keep a preview distinct from an exported artifact
A preview may use the current browser’s styles, fonts, screen size, and rendering behaviour. An exported HTML or text file can behave differently when opened elsewhere. If the final document matters, open the actual output in an appropriate target environment and inspect it there.
Use semantic headings and readable link labels when you control the content. That improves the document itself without claiming that a formatter has solved accessibility, legal, editorial, or security review.
Use a failure message as a useful stop point
If a tool refuses active content, sanitizes it, or shows a warning, that boundary protects the difference between helping with text and executing untrusted instructions. Copy the source into an appropriate development or security-review workflow when you actually need to test behaviour.
A local formatting result means the selected text was processed in the stated way. It does not certify a web page, validate a legal document, or approve a link destination.
Use a local tool