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Every format myartefacts shows: HTML, Markdown, Word, CSV, PDF and more
The file's extension decides what happens when you open it. HTML pages and apps run, documents are set as a page to read, spreadsheets become tables, and pictures and PDFs open as they are. A few formats a browser cannot draw by itself, and those download.
HTML pages, apps and decks
An .html or .htm file opens as the page it is, scripts and all. Buttons work, charts animate, a small app keeps running. On the sheet its thumbnail is a live preview of the page, drawn on a 1200 by 900 canvas and scaled down, so you see the real thing rather than an icon.
Every page runs in a sandbox, so its scripts can never reach your account or your session. Links that leave the page open in a new tab, while links to a heading on the same page still scroll. Forms and downloads from inside the page work as you would expect.
One thing worth knowing: an artefact is one file. A page that loads style.css or chart.js from the folder next to it on your disk will arrive without them. Ask your agent for a single self-contained file, with its styles and scripts inline, and it looks the same everywhere.
HTML covers more than pages. An agent can mark an HTML file as a Deck (slides built in HTML) or an App, which changes its kind on the sheet and in filters, not the way it opens.
Markdown, set as a document
A .md file is not shown as raw text. It is drawn as a document in the library's own type, with headings, lists, links, tables, task lists and footnotes, following GitHub Flavored Markdown. Code blocks carry their language as a label, with a Copy button, and Wrap when the lines run long.
A bar across the top lets the reader pick the text size, a reading column or the full width, and Page or Markdown to flip between the drawn page and its source. A document with three or more sections gets a contents list in the margin, so a long brief is easy to move around.
Raw HTML inside a Markdown file is shown as text, never run. If you want HTML to run, publish it as .html.
Word documents
A .docx opens as a document too. Headings, paragraphs, bulleted and numbered lists, quotes, tables, links and embedded pictures come across. Word's own fonts, colours and spacing are left behind, so the file reads like every other document in your library rather than like a printout of someone else's template.
If a file cannot be read as a Word document, the page says so plainly, and the original is still there to download. Other word-processor formats (.doc, .odt, .rtf, .pages) are filed as Doc but download rather than open. A .txt file opens as plain text.
CSV and TSV, as a table
A .csv or .tsv opens as a table. The first row is the header, columns that hold only numbers, money or percentages align right, and a line above the table counts the rows and columns. The separator is worked out from the first line, so comma, semicolon, tab and pipe files all open, and exports that arrive with a byte order mark or in Windows-1252 are read correctly.
Long files show their first 1,000 rows, so a big export still opens quickly. Files up to 512 KB also get a CSV or TSV switch in the bar, to see the raw text beside the table.
JSON opens as text in the browser. Spreadsheets in .xlsx, .xls, .ods or .numbers are filed as Data but download; ask for a CSV if you want to read the numbers in place.
SVG, images and PDF
SVG files open as drawn, in the same sandbox as HTML. PNG, JPEG, GIF, WebP, AVIF and BMP images open as they are, and an image is its own thumbnail on the sheet.
PDFs open in the browser's own viewer, fitted to the width with the toolbar and page rail hidden, and the thumbnail is the first page.
What downloads instead
Anything a browser cannot draw by itself downloads: PowerPoint and Keynote decks (.pptx, .ppt, .key, .odp), spreadsheets, archives, audio, video and the rest. The frame shows its kind where a preview would be, and the loupe says No preview for this file
with a link to download it. It is still a full artefact, with its title, project, versions and link.
Want a deck you can open from a link? Ask the agent for the slides as one HTML file and to publish it as a Deck, or for a PDF export. Both open straight away, on any phone.
At a glance
| Extension | Kind | Opens as |
|---|---|---|
| .html, .htm | HTML, or App or Deck | The page itself, sandboxed |
| .md, .markdown | Markdown | A document, with contents and source |
| .docx | Doc | A document |
| .txt | Doc | Plain text |
| .csv, .tsv | Data | A table, first 1,000 rows |
| .json | Data | Text |
| .svg | SVG | The drawing, sandboxed |
| .png, .jpg, .gif, .webp, .avif, .bmp | Image | The image |
| The browser's PDF viewer | ||
| .pptx, .ppt, .key, .odp | Deck | Download |
| .xlsx, .xls, .ods, .numbers | Data | Download |
| .doc, .odt, .rtf, .pages | Doc | Download |
| Anything else | File | Download |
Size, and a few good habits
- Up to 20 MB a file. That holds for agents and for files you drop onto the library yourself.
- Use a real file name with the right extension.
q3-report.mdbecomes a document; the same text saved asq3-reportwith no extension is just a File. - Keep it to one file. Inline the styles, scripts and small images a page needs.
- Large or binary files go up from disk. An agent asks for a one-time upload link and sends the file with curl, rather than pasting it into a tool call. See Publish a file that is already on disk.
- Text travels well. On a shared page, Copy as prompt pastes a text artefact whole when it is 100 KB or less, ready for any agent to read. See Share an artefact.
New here? What an artefact is explains the idea, and Connect Claude Code gets your first one in.