How to Preview Files on Mac Without Opening Them

Why "Just Open It" Isn't Always the Right Move

Opening a file to see what's in it costs more than it looks like. A 40 MB video launches QuickTime and starts buffering. A PDF spins up Preview or, worse, Acrobat. A random download from three weeks ago might not be what its filename claims, and double-clicking it to find out means waiting for an app, then closing that app, then going back to what you were actually doing.

macOS has had a fast path around this since 2007: Quick Look. Most people know the space bar trick. Fewer know the full set of shortcuts, which Finder views build previewing into the browsing experience itself, or exactly where Quick Look stops being useful. This guide covers all three, plus what changed for anyone who used to rely on a Quick Look plugin and found it broken after a macOS update.

Triggering Quick Look: Every Shortcut

Finder's Other Preview Views

Quick Look is a floating overlay you summon and dismiss. Finder also has three view modes that build previewing into the layout itself, useful when you're working through an entire folder rather than checking one file.

What Quick Look Still Can't Preview

None of this is a knock on a 19-year-old feature that still works well for the majority of file types. But it's worth being specific about where it stops, because these gaps are exactly what pushes people toward a third-party tool or, eventually, a dedicated app.

• Folders. Quick Look shows a folder icon, an item count, and a total size. It cannot show you the files inside without you opening the folder first. This is consistently one of the most-cited Quick Look complaints on Apple's own support forums.
• Archives (ZIP, RAR, 7z, TAR). Same problem as folders. Quick Look sees an archive as one opaque file. To know what's inside, you have to extract it, which defeats the point of "previewing without opening" entirely.
• Markdown files. A .md file previews as raw plain text, dashes, asterisks, and pound signs included, not as rendered headings, bold text, or bullet lists. If you write in Markdown regularly, this is one of the more noticeable native gaps.
• Code files. Source files preview as plain monospaced text with no syntax highlighting. Readable, but not the colored, indented view you get inside an editor or IDE.
• CSV and SQLite files. A CSV previews as comma-separated plain text rather than a table you can scan by eye. SQLite database files generally show "No preview available" entirely, since there's no built-in generator that understands the format.
• Some niche and legacy formats. Jupyter notebooks, EPUB books, certain 3D model formats, and older or unusual file types depend entirely on whether an app you've installed happens to register a Quick Look extension for them. Out of the box, macOS does not cover them.

The Sequoia+ Plugin Break

For years, the fix for most of the gaps above was a free Quick Look plugin: QLMarkdown for Markdown, QLStephen for plain-text files without extensions, QLVideo for extra codecs, and dozens more listed on sites like quicklookplugins.com. They used an old plugin format with the file extension .qlgenerator, and you installed them by dropping a file into ~/Library/QuickLook.

That stopped working with macOS 15 Sequoia. Apple removed support for the legacy .qlgenerator format, and previews built on it broke, including plugins for scientific and specialty file types that had worked reliably for a decade. The replacement is a modern App Extension format (files ending in .appex), built on the Quick Look Preview Extension and Thumbnail Extension APIs Apple introduced at WWDC back in 2019. Developers had roughly five years of overlap to migrate before the old format was cut off, and the well-maintained tools did. Plenty of smaller, side-project plugins never got updated, and they simply stopped rendering previews the moment their users upgraded.

As of macOS 26 Tahoe, current as of this writing, nothing about that has reversed. If a plugin still uses the old .qlgenerator format, it does not work, full stop, regardless of how well it worked on an older Mac. The practical upshot: before installing anything for extra Quick Look coverage, check that it was built (or rebuilt) for the App Extension format rather than assuming a plugin recommended in an old blog post still works.

Third-Party Tools That Fill the Gaps

If you regularly hit one of the gaps above, here's what actually works today, checked against each tool's own site rather than older roundups that may be citing discontinued pricing.

• Looq: Preview Files. Adds Markdown with Mermaid diagram and KaTeX math rendering, syntax highlighting across roughly 190 programming languages, CSV and SQLite shown as real tables, and archive and diff previews. Requires macOS 15 or later. $10 one-time (parcse.com); App Store lists it at $11.99. Also bundled in Setapp's all-app subscription.
• Unfold. Extends Quick Look to folders, archives, source code, Markdown with Mermaid diagrams, ebooks, and over 250 file types in total. Requires macOS 15.6 or later. $9.99 one-time (unfold.tools), no subscription, free trial available
• Glance. The original open-source all-in-one plugin (code, Markdown, archives, Jupyter, TSV) that many people still recommend from memory. As of this writing its GitHub repo has been archived and it was pulled from the App Store, so treat it as unmaintained rather than a safe current install; community forks exist but their Sequoia/Tahoe compatibility varies. Was free; original project inactive
• Folder Preview / Folder Quick Look. Smaller, single-purpose Mac App Store apps that specifically add folder-content previews to Quick Look. Folder Preview also handles ZIP, RAR, 7z, TAR, GZ, and BZ2 archives, so it covers both of the biggest native gaps in one small app. Folder Preview: $1.99 one-time. Folder Quick Look: $3.99 one-time (a separate, similarly named free "Folder Quick Look" app also exists on the App Store; check the listing carefully before buying).
• Folder Preview Pro. A more capable version from the same team behind Folder Preview, adding thumbnails inside the folder preview and the ability to copy or open files directly from the preview window without leaving Finder. Available on the Mac App Store and via Setapp; standalone price not published as of this writing
• Path Finder. Not a Quick Look plugin at all, but a full Finder replacement with its own built-in preview pane for PDFs, vectors, code, and video. Worth considering only if you want a broader Finder overhaul, not just better previews. $29.95/yr subscription, or a standalone license from $32.95 (1-year term) up to longer multi-year terms; free trial available

A general pattern worth noting: the actively maintained options (Looq, Unfold) are one-time purchases around $10, not subscriptions, and both explicitly require macOS 15 or later since they're built on the modern extension format described above. Anything still advertising a classic .qlgenerator install method is worth double-checking before you rely on it.

Built-In vs Third-Party, Side by Side

Where Quick Folder Preview Fits In

We build Quick Folder Preview, a Mac utility aimed squarely at the biggest gap covered above: seeing what is actually inside a folder or an archive without opening it. It is not available yet. The plan is a drag-and-drop, folder-first take on instant preview, for macOS 11 and later on both Intel and Apple Silicon, with no price or release date locked in yet.

We are not asking you to wait for it. Everything in this guide, the space bar, Option+Space, the Finder preview views, and the third-party tools above, works today and will keep working regardless of when Quick Folder Preview ships. If folder-and-archive preview specifically is a gap you hit often and you want to know when a purpose-built fix is ready, the waitlist on the product page is the way to hear about it first.

Sources & Further Reading

Frequently Asked Questions

The Bottom Line

For the vast majority of files, the space bar is still the fastest way to see what something is on a Mac. Learn Option+Space for full screen and the arrow keys for cycling a selection, and you've covered most of what Quick Look can do. The real gaps, folders, archives, rendered Markdown, syntax-highlighted code, and table views of CSV or SQLite data, are specific and well understood at this point, and small, inexpensive tools already exist for most of them. Start with what's already on your Mac, add a third-party tool only for the specific gap you actually hit, and treat anything still built on the old .qlgenerator format as retired.

Looking for more Mac productivity guides? Browse every 1dot.ai guide, see how we approach accessing recent files faster on Mac, or check Quick Folder Preview's product page for the waitlist.