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.HTM file extension

To open .HTM files on Windows, double-click the .htm file to open it in your default web browser.

To open a .htm file, use a web browser (to view it as a web page) or a text editor (to read/edit the HTML source). If double-clicking doesn’t work, set a browser as the default app for .htm.

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Last updated: June 11, 2026 · Reviewed by Julian Stricker

What “reviewed” means on this page
  • Format fit: whether the “what is this file?” description matches common real-world use of the extension, including category, typical MIME types, and aliases.
  • Opening paths: whether Windows / macOS / Linux steps read plausibly for current OS dialogs and default apps; we remove fantasy menus and unsafe shortcuts.
  • Security framing: whether risk notes match the extension class (for example executables vs plain data) and whether affiliate wording does not contradict the security section.
  • Sources and further reading: whether external links point to vendors, standards bodies, or other primary references where possible; we avoid inventing details we cannot ground.
  • Limits: this is clarity and safety-messaging QA, not a guarantee that every statement is exhaustive or that every binary you download is harmless.

Full methodology in the Imprint — The Imprint also states where AI is used and what that does—and does not—replace.

Open on your device

Choose your operating system for a dedicated step-by-step opening guide.

How to open .HTM files

Use these platform-specific instructions to open .HTM files safely.

Windows

  1. Double-click the .htm file to open it in your default web browser.
  2. If it opens in the wrong app: right-click the file → Open with → choose a web browser (or a text editor to edit the source).
  3. For troubleshooting, open it from a browser using File → Open (or drag the file into the browser window).
Full Windows guide

Mac

  1. Double-click the .htm file to open it in your default browser.
  2. To choose a specific app: Control-click → Open With → pick a browser to view or a text editor to edit.
  3. If the page looks broken, try opening it in another browser to compare rendering.
Full Mac guide

Linux

  1. Double-click the .htm file in your file manager to open it in the default web browser.
  2. If needed: right-click → Open With → select a browser (view) or a text editor (edit).
  3. If file type detection is wrong, check that the system recognizes it as text/html via your desktop’s MIME/file association settings.
Full Linux guide

iOS

  1. In the Files app, tap the .htm file to preview; if it doesn’t display properly, share/open it in a web browser app to view it.
Full iOS guide

Android

  1. In your file manager or Downloads, tap the .htm file and choose a web browser to open it; if no browser option appears, open the browser and use its “Open file” feature if available.
Full Android guide

Security notes

  • Treat .htm files as potentially active content: they can include scripts and load external resources, so opening untrusted .htm files may expose you to phishing-style interfaces or unexpected network requests.
  • If the .htm file came from an unknown source, consider opening it in a text editor first to inspect links and script tags before rendering it in a browser.
  • Be cautious with .htm files that prompt you to enter passwords or personal data—HTML can mimic legitimate login pages even when opened locally.
  • Browsers apply security restrictions differently for local files (file://) versus web-hosted pages; do not relax security prompts for untrusted documents.

If you did not expect this file

This extension is usually plain data, text, or structured content—not a program by itself. The practical risk is social engineering (a scam attachment or misleading filename). For trusted senders you rarely need heavy-handed antivirus wording; use these tools when you want an extra check on unexpected downloads.

Avast

Avast offers free and premium antivirus software that protects against viruses, malware, ransomware, and phishing. Scan files before opening them to ensure safety.

Norton

Norton 360 delivers comprehensive antivirus protection, VPN, and identity theft monitoring. Scan files for threats before opening to keep your device secure.

We may earn a commission when you use affiliate links. This supports our free file extension guides.

Can't open this file?

These are the most common causes and fixes when .HTM files fail to open.

Common reasons

  • The .htm file opens as plain text instead of a web page
  • The page looks broken (missing images/CSS) when opened locally
  • Browser warns about blocked scripts or mixed/unsafe content
  • Double-clicking does nothing or opens the wrong app

Fix steps

  1. Use Open with to select a web browser and (if offered) set it as the default for .htm.
  2. Alternatively, drag the .htm file into an open browser window.

OS-specific troubleshooting

What is a .HTM file?

.htm is a common filename extension for HTML documents and is widely used as a shorter variant of .html. When served on the web, these files are typically labeled with the media type text/html. An .htm file is generally plain text containing HTML markup, and may reference or include scripts and external resources.

Background

HTML (HyperText Markup Language) is the standard markup language used to structure documents on the web. Files commonly use the .html extension, and .htm is a widely used abbreviation for the same kind of document.

Common MIME types: text/html

Further reading

Authoritative resources for more details on the .HTM format.

Common .HTM issues

The .htm file opens as plain text instead of a web page

The file is being opened in a text editor, or the system’s file association for .htm isn’t set to a browser.

  1. Use Open with to select a web browser and (if offered) set it as the default for .htm.
  2. Alternatively, drag the .htm file into an open browser window.

The page looks broken (missing images/CSS) when opened locally

The .htm file may depend on additional files (images, stylesheets, scripts) that weren’t saved or aren’t in the expected relative paths.

  1. Verify that any referenced files (e.g., folders for images or CSS) are present alongside the .htm file as expected.
  2. If it was exported or downloaded, re-export/re-download ensuring “complete webpage” (HTML plus assets) was saved, not just the HTML file.

Browser warns about blocked scripts or mixed/unsafe content

HTML can include or reference script content; browsers may restrict scripts or local file access for safety, especially for local files.

  1. If you don’t trust the source, do not bypass the warning—view the file as text instead.
  2. If it is your own page, test by serving it from a local web server rather than opening via file://, which can change security and loading behavior.

Double-clicking does nothing or opens the wrong app

The default application mapping for .htm may be missing or misconfigured.

  1. Manually open it in a browser using Open with.
  2. Reset the default app association for .htm to a web browser in your system settings.

FAQ

What is the difference between .htm and .html?

For most purposes there is no functional difference—both commonly indicate an HTML document. .htm is a shorter abbreviation that is widely used.

What MIME type is associated with .htm files?

HTML documents are commonly labeled with the media type text/html.

Can I convert a document to .htm by renaming the file extension?

No. Renaming only changes the filename suffix; it does not turn the content into valid HTML. Use an export or conversion feature that actually produces HTML.

Why does my .htm file look different in different browsers?

Browsers can render some HTML/CSS features differently, and scripts may behave differently depending on browser security settings—especially when opened as a local file.

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