HTM vs RST
A detailed comparison of HTML Document (short) and reStructuredText — file size, quality, compatibility, and which format to choose for your workflow.
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Technical Specifications
| Specification | .HTM | .RST |
|---|---|---|
| MIME type | text/html | text/x-rst |
| Extension | .htm | .rst |
| Standard | HTML Living Standard (WHATWG) | — |
| Alias of | .html | — |
| Origin | DOS 8.3 filename limit | — |
| Toolchain | — | Docutils, Sphinx, Read the Docs |
| Encoding | — | UTF-8 |
| Related formats | — | MyST (Markdown + RST directives) |
Strengths Comparison
.HTM Strengths
- Identical content to .html in every respect.
- Universally supported by every browser and server.
- 8.3 compatibility for antique DOS/Windows shares.
.RST Strengths
- Rich directives for admonitions, code, math, and custom elements.
- Cross-references work within and across documents.
- Sphinx ecosystem offers best-in-class Python docs output.
- Standardized as part of Python PEP infrastructure.
- Plain text, version-controllable.
Limitations
.HTM — Limitations
- No real reason to use .htm over .html in 2026.
- Inconsistent with modern naming conventions.
- Mixed extensions within one site confuse static-site generators.
.RST — Limitations
- Syntax denser than Markdown — higher learning curve.
- Less widely adopted than Markdown outside Python world.
- Multiple directive dialects (Sphinx, Docutils, custom) create fragmentation.
- MyST (Markdown + Sphinx) has pulled many Python projects toward Markdown.
Frequently Asked Questions
HTM (HTML Document (short)) is a document format used to store paginated text, with optional formatting, tables, images, hyperlinks, headers and footers. It sits in the documents & text family and is typically associated with a specific office suite or publishing pipeline that defined the format and ships the canonical reader.
RST (reStructuredText) is a document format used to store paginated text, with optional formatting, tables, images, hyperlinks, headers and footers. It sits in the documents & text family and is typically associated with a specific office suite or publishing pipeline that defined the format and ships the canonical reader.
Modern office suites — Microsoft Word, Google Docs, LibreOffice Writer, Apple Pages — open most HTM files with reasonable fidelity. If your installed software does not support HTM, convert to DOCX or PDF first using KaijuConverter; both open in virtually every reader, including free online viewers.
Modern office suites — Microsoft Word, Google Docs, LibreOffice Writer, Apple Pages — open most RST files with reasonable fidelity. If your installed software does not support RST, convert to DOCX or PDF first using KaijuConverter; both open in virtually every reader, including free online viewers.
Upload the HTM to KaijuConverter and pick DOCX, PDF, ODT, RTF, HTML, Markdown, or plain text. Our pipeline runs LibreOffice headlessly plus pandoc for text formats — the same engines behind professional document pipelines. Styles, tables, images, and hyperlinks survive the conversion intact.
Yes, to a high degree. Standard fonts, headings, lists, tables, images, hyperlinks and page structure transfer cleanly. Custom fonts substitute to the closest match if not embedded; obscure layout features unique to HTM (frames, legacy macros) may flatten to static content in the target format.
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