Free online HTML to HTM converter

A legacy web host, publishing system, or Windows-era application may accept a page only when its filename ends in .htm. Since .htm and .html identify the same web document format, the usual conversion changes the filename extension rather than rewriting the page.

What HTML is

HTML (HyperText Markup Language) is the text-based markup format used to structure web pages and local browser documents. An HTML file can contain headings, paragraphs, links, lists, tables, forms, images, metadata, and references to CSS and JavaScript files.

Web developers, web editors, content-management systems, static-site generators, and server applications create HTML files. Browsers such as Chrome, Firefox, Safari, and Edge open them directly, while Visual Studio Code, Notepad++, and other text editors can edit their source. The usual extension is .html, although .htm is also valid.

What HTM is

HTM is not a separate markup language or a reduced form of HTML. It is the same HTML document format identified by the three-character .htm extension.

The shorter extension can satisfy legacy software, hosting systems, publishing workflows, or filename conventions that expect three-character extensions, including older sites using names such as index.htm. Modern browsers normally process .htm and .html identically. The extension does not make a file smaller, faster, or more compatible with HTML features.

How to convert HTML to HTM

Renaming the extension is the preferred method because it changes the filename without changing the document bytes, markup, encoding, or linked resources.

1. Back up the original file, particularly if it belongs to a published website, source-control repository, or automated build.
2. On Windows, show extensions with File Explorer → View → Show → File name extensions. This prevents changing only the visible name while leaving the real .html extension unchanged.
3. Rename a file such as home.html to home.htm, then confirm the extension-change warning.
4. Open the renamed file in a browser and check the page, images, stylesheets, scripts, forms, and links.

On macOS or Linux, rename the file in the file manager or run mv home.html home.htm in a terminal. In Windows PowerShell, run Rename-Item home.html home.htm. For multiple files, use a batch-renaming tool or a carefully tested shell script, and preserve each file's original base name.

An HTML or text editor can save a second copy with File → Save As: enter a filename ending in .htm, choose HTML or plain text if a file-type option is provided, and disable any setting that automatically appends another extension. This method may alter line endings, encoding, or formatting, so direct renaming is safer when the content does not need editing.

You can also convert the file for free on 101convert.com without installing software, but an extension-only change is sufficient for an ordinary HTML document.

Compatibility and limitations

Renaming does not modify HTML syntax, character encoding, CSS, JavaScript, images, or relative asset paths. Relative references normally continue to work when the renamed file and its assets remain in the same directories.

Update links, navigation menus, sitemap entries, rewrite rules, redirects, canonical URLs, and other references that still point to the old .html filename. On case-sensitive servers, also preserve the exact capitalization used by filenames and links.

A web server may assign different routing, MIME, caching, or access rules to .htm and .html; check the server configuration if the renamed page downloads instead of opening, returns an error, or stops receiving the expected server-side processing. Renaming a file does not convert PHP, template syntax, framework routes, or other server-side code, and those systems may require configuration changes.

Do not use a word processor for this task. It may insert document-format markup or save a file that is not valid HTML. If the source is already valid HTML, changing the suffix is the only conversion normally required.