File Formats

Zelares is a Markdown-first editor. Markdown and plain-text files can be edited directly, while supported documents, spreadsheets, images, videos, and audio files can be opened in a read-only preview.

Previewing a file does not convert or modify the original. The file remains stored in its original format, including files stored privately in the project's object storage.

Editable formats

Extensions	Access	Use for
`.md`, `.mdx`, `.mdc`	Edit and preview	Notes, documentation, knowledge bases, and collaborative writing.
Files without an extension	Edit as plain text	Simple text notes and imported plain-text content.

Preview formats

The following formats can be opened inside the Zelares editor. Their contents are displayed without changing the original file, but they cannot currently be edited directly.

Type	Extensions	Preview features
Images	`.avif`, `.bmp`, `.gif`, `.jpeg`, `.jpg`, `.png`, `.svg`, `.webp`	Image preview, animated image playback, transparency, fit-to-pane, zoom controls, dimensions, and file size.
PDF	`.pdf`	Continuous pages, thumbnails, table of contents, page navigation, text selection, links, and zoom controls.
Word documents	`.docx`, `.dotx`, `.docm`, `.dotm`	Paginated preview, page navigation, headers, footers, notes, embedded images, and zoom controls.
Excel and spreadsheets	`.xlsx`, `.xls`, `.xlsm`, `.xlsb`, `.xlt`, `.xltx`, `.xltm`, `.ods`, `.fods`, `.csv`, `.tsv`	Worksheet tabs, formatted values, formulas, merged cells, row and column headers, keyboard navigation, and zoom controls.
Video	`.mp4`, `.m4v`, `.webm`, `.ogv`, `.mov`	Playback, seeking, volume, fullscreen, duration, dimensions, and native browser controls.
Audio	`.mp3`, `.m4a`, `.m4b`, `.aac`, `.wav`, `.wave`, `.ogg`, `.oga`, `.opus`, `.weba`, `.flac`	Playback, seeking, volume, duration, and native browser controls.

Preview limitations

Preview-only files cannot currently be edited or converted inside Zelares.
Image decoding, including AVIF, WebP, SVG, and media playback, depends on the user's browser and operating system.
Uploaded SVG files are displayed as image resources and are not inserted as inline HTML.
Word pagination and formatting can differ slightly from Microsoft Word.
Macros inside macro-enabled Word or Excel files are never executed.
Spreadsheet formulas display stored results and are not recalculated by Zelares.
Large spreadsheets may show a limited number of rows and columns to keep the editor responsive.
PDF table-of-contents navigation is available only when the PDF contains an embedded outline.
Video and audio playback depends on codecs supported by the browser and operating system.

Not supported yet

Formats that cannot currently be opened include legacy Word documents such as .doc, rich-text files such as .rtf, OpenDocument text files such as .odt, and presentation formats such as .ppt and .pptx.

Naming tips

Use clear names such as README.md, Meeting Notes.md, or Project Budget.xlsx.
Keep the correct extension so Zelares can identify the file and select the appropriate preview.
Keep internal Markdown links stable by avoiding unnecessary renames after other notes link to the file.
Use folders to organize related Markdown files, documents, spreadsheets, images, and media.