Preview and Viewers

Some text files have a picture: Markdown, HTML, SVG and tables. The Editor can show that picture beside the text or on its own. Files that are not text at all — images, PDFs, video, audio and 3D models — open in a viewer instead of as text. This page covers both.

Preview a file#

Preview is available for:

• Markdown — rendered as GitHub-flavored Markdown, including tables and task lists. Code blocks fenced as mermaid are drawn as Mermaid diagrams.
• HTML — the page as written, for any file the Editor colors as HTML, such as .html, .htm, .xhtml or .vue.
• SVG — the drawing as an image.
• CSV and TSV (also .tab) — a table.

To show it, choose Show Preview in the toolbar (the eye; on Apple Vision Pro, in the row of controls below the window). The button cycles through three states:

1. Show Preview — the preview appears beside the text.
2. Preview Only — the preview replaces the text.
3. Hide Preview — back to the text alone.

On iPhone: there is no room beside the text, so the button switches between the text and the preview alone. A file with an extremely long line — such as an SVG exported as a single line — opens in its preview first, because the text view cannot draw it; choose Hide Preview to see the text.

The preview follows your edits, not the saved file. It redraws a moment after you stop typing.

Diagrams with Mermaid#

Write a fenced code block with the language mermaid in a Markdown file:

```mermaid
graph LR
  alpha --> bravo
```

The preview draws the diagram in the light or dark style that matches your appearance. If a diagram has an error, the preview shows a line beginning Mermaid: with the reason at the end of the page.

What a preview can load#

A preview is kept to the file and its surroundings:

• Images and other files referenced with a relative path are read from the file's project, or from its folder when it has no project. For a file on a server, they are read over the same connection. Files outside that folder are not loaded.
• Nothing is loaded from the internet.
• Scripts in an HTML file do not run, and script, HTML and WebAssembly files beside it are never loaded. The only script a preview runs is the Mermaid copy built into the app, and only for Markdown. HTML written inside a Markdown file is drawn, with its scripts blocked.
• Choosing a web or email link opens it in your browser or mail app. Links with other kinds of address do nothing.

Tables#

A CSV or TSV preview is a scrolling table. When the first row looks like a header — every cell filled and none of them a number — it is used as column names. Otherwise the columns are lettered A, B, C, like a spreadsheet. Choose a column name to sort by it; choose it again to reverse the order. The table shows the first 10,000 rows and says so when the file has more.

Images, PDFs, video and audio#

A file whose contents are an image, a PDF, a video or audio opens in a viewer in its tab. The Editor decides by the file's contents first and its extension second, so a picture with the wrong extension still opens as a picture. SVG files are text and open in the Editor with a preview.

On Apple Vision Pro, iPad and iPhone:

• An image fits the tab. Pinch to zoom, up to eight times, and double-tap to switch between fitted and twice the size.
• A PDF opens in a scrolling page view.
• Video and audio open in a player.

On Mac: the viewer is Quick Look, with its own zoom, paging and playback controls.

A viewer is never edited or saved.

3D models#

USDZ, USD and Reality files open in a 3D viewer in their tab. As with pictures, the Editor goes by what the file contains, so a USDZ saved under another name still opens as a model. A Reality file is known by its name.

• On Mac, iPad and iPhone: the whole model is framed in the tab. Drag to turn it, and scroll or pinch to move closer.
• On iPad and iPhone: View in AR opens the model in AR Quick Look, to stand it in the room around you.
• On Apple Vision Pro: the model stands in the window, and as the file opens, Apple's Quick Look also opens it in a volume of its own that you can walk around. View in 3D opens the volume again.

AR Quick Look and the Vision Pro volume take USDZ and Reality files only, so a USD file stays in its tab, without View in AR or View in 3D. A USD file written as text (it starts with #usda) also has Open as Text, to edit it in the Editor. If a model can't be shown, the tab says Can't Show This Model and why.

Files that are not text#

Any other binary file shows This File Isn't Text with its size. Choose Open as Text to open it in the Editor anyway.

Large files#

The Editor reads a file whole, up to 64 MB.

• On this device: a larger image, PDF, video, audio or 3D model still opens in its viewer, which reads it from the disk. A larger text or other file is not opened, and the message says so; open it in another app. Something that is not a file at all, such as a named pipe, is not opened either.
• On a server: a file larger than 64 MB can't be opened in the Editor. For an image, PDF, video, audio or 3D model file, Download this file? shows its size first, with Download and View and Cancel, but the file still doesn't open.