Showglass

Support

Showglass needs macOS 26 or later, on Apple silicon or Intel.

Turn on the extensions

macOS asks you to turn on Showglass once, in System Settings: two entries, Showglass Previews and Showglass Thumbnails. Until you do, Quick Look keeps showing its own previews.

  1. Install Showglass from the Mac App Store and open it once, so macOS knows about its extensions.
  2. Open System Settings, then General › Login Items & Extensions.
  3. Choose Quick Look, then turn on Showglass Previews and Showglass Thumbnails.
  4. Select a file in Finder and press Space.

Showglass can take you there: in the app, open Settings › General and choose “Open Login Items & Extensions…”. To try it on sample files, choose Help › Welcome to Showglass and export the sample files to a folder. There is one per family.

If a preview still looks like the macOS one, check that the type isn't one macOS keeps for itself. Restarting Quick Look can also help: type qlmanage -r in Terminal and press Return.

Finder thumbnails

Showglass draws Finder thumbnails for 15 types, such as ZIP and YAML files. The app checks its thumbnail extension with a sample .yaml file. If its sidebar says “Thumbnails are off”, turn Showglass on in the same Quick Look list as above, then choose Check Again in Settings › General.

Finder keeps thumbnails it has already drawn for a while, so older files can take a moment to change.

Questions

Does Showglass connect to the internet?

Your files never leave your Mac. The Quick Look extensions, which draw the previews and thumbnails, have no network access, and previews don't load remote images. The app sends anonymous usage counts and crash reports; crash reports are sent only with your permission. You can turn them off in Settings. See the privacy policy.

Why can't I search inside a preview?

Quick Look doesn't pass typing to previews, so Showglass has no search field inside them. Search lives in the app: the format gallery and “Can Showglass open…?” both accept typing. Copying with ⌘C and selecting all with ⌘A work in previews.

Can I switch a family off?

In Settings › Families, each family has a Rich view switch. Turned off, that family shows the plain view: highlighted source, a basic font specimen or a card of file facts. Once Showglass claims a type, macOS can't take it back, which is why the switch is Rich view rather than on and off.

Why does my .ts file show a video preview?

To macOS, files ending in .ts or .mts are video. Showglass previews TypeScript in .tsx and .cts files.

Why doesn't my .env file get a preview?

Bare dotfiles such as .env and .zshrc have no extension, so macOS treats them as generic data. Files with a real ending, such as prod.env or .env.local, are previewed, with values hidden until you reveal them.

Does Showglass play video or audio?

No. Media macOS can play stays with its own player. For WebM and Matroska files, Showglass shows the tracks, codecs and chapters.

What happens with very large files?

Showglass reads only part of them and says so in one plain sentence at the top of the preview, so you always know what was cut.

Which languages does the app use?

English.

How do I remove Showglass completely?

Delete Showglass from your Applications folder. Its settings live in its own folders in ~/Library/Containers and ~/Library/Group Containers; an app cleaner, or removing those folders, deletes them too.

Types Showglass can't preview

Measured on macOS 27.0.1 in October 2026. Showglass needs macOS 26 or later.

macOS keeps its own previewers for these types, and third-party extensions can't replace them. When you press Space on one of them, you see Apple's preview, with or without Showglass.

  • Plain text: .txt files and files with no extension, such as README or Makefile (dotfiles are different: see below)
  • Rich text: RTF and RTFD
  • Web pages: HTML and XHTML
  • SVG graphics
  • Images: PNG, JPEG, HEIC, WebP, AVIF, GIF, TIFF, PSD, RAW and the other image types macOS opens
  • PDF
  • CSV spreadsheets
  • Microsoft Office: Word, Excel and PowerPoint
  • OpenDocument files, such as .odt
  • iWork: Pages, Numbers and Keynote
  • Contacts and calendars: vCard and iCalendar
  • 3D: STL, OBJ and PLY

We haven't tested the types below, but we expect the same:

  • Web archives: .webarchive
  • 3D: USD and USDZ, Reality, Alembic and MaterialX
  • Crash reports: .ips
  • Illustrator and EPS: .ai and .eps

Showglass doesn't preview these either, for its own reasons:

  • Disk images: .dmg. Showglass never mounts anything.
  • Figma (.fig) and DjVu (.djvu) files.
  • Bare dotfiles such as .env, .envrc and .zshrc: no preview. They have no extension, so macOS treats them as generic data. Files with a real ending, such as prod.env or .env.local, are previewed, with values hidden until you reveal them.

Two file endings mean something else to macOS:

  • TypeScript files ending in .ts or .mts are video files to macOS, so they get the video preview. Showglass previews .tsx and .cts.
  • Files ending in .key are Keynote presentations to macOS. Showglass never previews private keys.

Folders get a Showglass preview (what's inside, with an image grid for folders of photos), but folder icons stay macOS's: Finder draws them itself, so Showglass can't offer a thumbnail for a folder, a volume or a package. Packages such as apps, .rtfd documents and Xcode projects keep the system preview; Showglass never opens them, in the Finder or inside a folder it previews.

Audio and video that macOS plays stay with macOS's own player, because Showglass has no player. For WebM and Matroska files (.webm, .mkv, .mka), Showglass shows a card with the tracks, codecs and chapters. It doesn't play them.

Where Showglass draws Finder thumbnails

Showglass draws the preview you see when you press Space. Finder thumbnails are a bonus that macOS allows only for some types:

  • Archives: ZIP, TAR, gzip (.gz, .tgz), bzip2, xz, 7-Zip, Java archives (.jar, .war) and iOS apps (.ipa)
  • Text: YAML, TOML¹, INI¹, CSS, WebVTT subtitles, NDJSON and .strings¹ files

¹ Measured with Xcode installed, which registers those file types. On a Mac without Xcode, Showglass registers them itself; we expect the same result and check it on the release build.

Everywhere else, including source code, Markdown, JSON, fonts, 3D models and folders, macOS draws the Finder thumbnail and Showglass draws the preview.

Measured on macOS 27.0.1 in October 2026; the minimum is macOS 26, which we check separately. We check the whole list again on the release build before launch.

Contact

Write to support@vpolabs.com, or use Send Feedback… in the app. It opens a draft in your own Mail app; you read it and decide whether to send it. You can attach a short diagnostics file (app and macOS versions, which extensions and families are on, whether Pro is unlocked). It never contains file names, paths or file contents.