Free online HTM to HTML converter

Some hosting systems, editors, and publishing workflows require the .html extension even though a browser can usually open the same document as .htm. The change is normally an extension rename, but saving a separate copy can help when the original filename must remain available.

What the HTM format is

.htm is a three-character filename extension for an HTML document. It was widely used when older operating systems and applications imposed three-character extension limits. Web browsers, code editors, static-site generators, and web-authoring software can create or open HTM files.

An HTM file normally contains plain-text HTML markup, including headings, links, tables, forms, styles, and scripts. Images, stylesheets, scripts, and fonts referenced by relative URLs remain separate files; changing the extension does not embed or copy those assets.

What the HTML format is

.html is the longer, commonly used extension for the same HTML document type. Websites, documentation systems, local web pages, and static hosting platforms frequently use it. The extension makes the file type more recognizable and may satisfy software or hosting rules, but it does not change the HTML language, browser rendering, or document contents.

Browsers generally handle .htm and .html identically. A web server can serve either extension incorrectly if its MIME configuration, routing rules, or default-document settings are wrong; HTML files should normally be served with the text/html media type.

How to rename an HTM file

1. Back up the original file.
2. Enable visible filename extensions in the file manager. In Windows File Explorer, use View → Show → File name extensions.
3. Rename page.htm to page.html, then confirm the extension change. Do not rename it to page.html.htm.
4. Open the new file in a browser and check its links, images, stylesheets, and scripts.

On macOS or Linux, run mv page.htm page.html in the file's directory. For a batch rename in PowerShell, use Get-ChildItem -File -Filter *.htm | Rename-Item -NewName { $_.BaseName + '.html' } in a copied folder first, and check for existing files with the target names.

How to save a separate HTML copy

Open the file in a plain-text or web editor such as Visual Studio Code or Notepad++. Choose File → Save As, enter a name ending in .html, and prevent the editor from adding .txt. Preserve the source encoding when possible; select UTF-8 only after confirming that the original text is decoded correctly. Saving can change encoding, line endings, or whitespace, so renaming is safer when no content change is needed.

For a simple extension conversion without installing software, upload the file to 101convert.com, choose the HTML output if requested, and download the resulting .html file. Test the downloaded file with its associated asset folders.

Compatibility and quality checks

Renaming does not repair invalid markup, modernize obsolete HTML, change character encoding, move linked assets, or rewrite URLs. Keep the original directory structure while testing because paths such as css/site.css and images/logo.png are relative to the document location.

If other pages, navigation menus, sitemaps, build scripts, bookmarks, or deployment settings refer to the old filename, update those references. On a server, either retain page.htm or configure a redirect to page.html to avoid broken links, and add the new name to the server's default-document configuration if it should load automatically.