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Task 294: .HTM File Format

Task 294: .HTM File Format

thinkmelt@protonmail.com

• 7 min read

File Format Specifications for .HTM

The .HTM file format is an extension variant of HTML (HyperText Markup Language), which is a standard markup language for creating web pages. It is identical to .HTML files in structure and content; the .HTM extension originated from older operating systems (like DOS/Windows 3.x) that limited file extensions to three characters. There is no difference in the format itself—.HTM files are plain text files containing HTML markup, scripts, and styles. They are not a binary format with fixed headers or encoded properties.

The official specifications are defined by the WHATWG (Web Hypertext Application Technology Working Group) in the HTML Living Standard and by the W3C (World Wide Web Consortium) in versions like HTML5. Key aspects include:

  • Text-based format, typically encoded in UTF-8 or ASCII.
  • Starts with a DOCTYPE declaration (e.g., <!DOCTYPE html>) followed by <html>, <head>, and <body> elements.
  • No magic number or binary signature; identification is based on content (markup tags) and MIME type (text/html).
  • Files can include embedded CSS, JavaScript, and references to external resources.

Since .HTM/HTML is a text format without a structured binary header or embedded metadata specific to the format (unlike formats like PNG or PDF), there are no "intrinsic" format-specific properties encoded within the file itself that require decoding. Any "properties" are either derived from parsing the HTML content (e.g., meta tags) or from the file system's metadata (e.g., size, timestamps). Given the query's emphasis on "intrinsic to its file system," I interpret this as referring to standard file system metadata attributes, which are common to all files but can be retrieved for .HTM files.

List of all the properties of this file format intrinsic to its file system:

  • File Name: The name of the file, including the .htm extension.
  • File Size: The size of the file in bytes.
  • MIME Type: The content type, typically "text/html".
  • Last Modified Time: The timestamp when the file was last modified.
  • Creation Time: The timestamp when the file was created (availability depends on the OS/file system; e.g., available on Windows NTFS, but may map to birth time on Unix).
  • Last Access Time: The timestamp when the file was last accessed (may not be updated on all systems).
  • Permissions: The file access permissions (e.g., read/write/execute for user/group/others; represented as octal mode on Unix-like systems).
  • Owner User ID: The user ID of the file owner (UID on Unix-like systems).
  • Owner Group ID: The group ID of the file owner (GID on Unix-like systems).
  • Inode Number: The inode number (unique identifier on Unix-like file systems).
  • Device ID: The device ID where the file resides (on Unix-like systems).
  • Number of Hard Links: The count of hard links to the file (on Unix-like systems).

Note: These are file system metadata, not encoded in the .HTM file content. Availability varies by OS (e.g., Windows vs. Linux) and runtime environment (e.g., browser JS has limited access). For .HTM specifically, the MIME type is a key identifier, but it's inferred rather than stored.

Two direct download links for files of format .HTM:

Ghost blog embedded HTML JavaScript for drag-and-drop .HTM file to dump properties:
(This is a self-contained HTML snippet with embedded JavaScript that can be embedded into a Ghost blog post or page via the HTML card/block. It creates a drag-and-drop zone. When a .HTM file is dropped, it dumps the available file system properties to the screen. Note: Browser JS limits access to name, size, type, and lastModified; other properties like permissions or owner are not accessible client-side for security reasons.)

Drag and Drop .HTM File Analyzer
Drag and drop a .HTM file here