Press `Space` — take a gander

Q: Can Gander draw Mermaid diagrams inside Markdown?

Yes. A fenced code block marked mermaid is drawn as a diagram inside the rendered page, and .mmd or .mermaid files open as diagrams on their own.

Gander turns the Quick Look preview in Finder into a real viewer for the files developers open every day: Markdown with Mermaid diagrams, JSON, CSV, SQL, SQLite, Jupyter notebooks, logs, .env files and code in 30 languages. No editor, no switching apps, and Markdown exports to PDF or Word, CSV to Excel, in a click.

Get it on the Mac App Store Watch the 30-second tour

Free, with no in-app purchases. For macOS 15 or later. Made by 65FN LLC.

Try it: click a file, then press Space.Try it: tap a file to preview it.

README.md rendered as Markdown: the Nimbus Weather API heading, a green Tip alert and the start of a Mermaid flowchart.

See it in 30 seconds

Every preview in the video is a real render from Gander’s Quick Look extension.

What the video shows

0:00A Finder window shows a sample project called nimbus, and README.md is selected.
0:02Space is pressed, and Quick Look opens README.md as rendered Markdown.
0:04The README scrolls past a Mermaid flowchart, a table and a task list.
0:06Mermaid files open as diagrams: a sequence diagram, a Gantt roadmap and a git graph.
0:10nimbus.sqlite opens read-only on the Content tab: rows from the api_keys table, then the cities table.
0:13weekly_report.sql opens Formatted, and the query scrolls by with its keywords right-aligned in one column.
0:15A JSON Lines log shows one record per line, and one record expands as formatted JSON.
0:19A .env file opens with every value hidden, Show values reveals them, then they are hidden again.
0:23YAML, TOML, Terraform, a ZIP archive and a JSONC config with comments preview in turn.
0:26Closing title: “Press Space — take a gander”.

A viewer for each file in your project

Gander gives each kind of file a preview built for it, with a copy button for exactly what it shows. Previews follow your Mac’s light or dark appearance, and every image on this page is a real render from the app.

Markdown, rendered the way GitHub shows it

README files open rendered, with the Raw source one click away. Everything in GitHub-flavoured Markdown works, plus the extras that usually need a browser.

Tables, task lists, strikethrough and autolinks
Math with $…$ and $$…$$, and footnotes
GitHub alerts as coloured boxes (Note, Tip, Important, Warning and Caution), and quotes with GitHub’s grey bar
Code blocks coloured by language, with long lines kept whole and a copy button
:emoji: shortcodes, and mermaid code blocks drawn as diagrams

Read the guide →

README.md rendered: the Nimbus Weather API title, a Tip alert and a Mermaid flowchart of how a request flows.

The same README scrolled to an Endpoints table and a Release checklist with ticked and unticked tasks.

Export Markdown to PDF, Word, RTF or HTML

In a Markdown preview, press Export, next to the copy button. Pick the format, the paper size (A4 or US Letter) and page numbers, and save. Diagrams, tables, math, footnotes and pictures come along, and export is free.

Or open the file in Gander: a window with the whole document that reloads as you edit, with File › Export (⌘E for PDF)
An Export Markdown action for Shortcuts
Everything stays on your Mac: images on the web are never fetched

Read the guide →

PDFVector diagrams, bookmarks and working links
Word (.docx)Real headings, lists, tables and footnotes
RTFFormatted text, tables and pictures for TextEdit, Pages or Word
HTMLOne self-contained file, with the diagrams and pictures inside

CSV and TSV as a real table, then on to Excel

Delimited files open as a spreadsheet grid: row numbers, the header, numbers right-aligned, and any separator or encoding Excel writes, including decimal commas. One click turns the file into an Excel workbook (.xlsx), every row of it, and that’s free too. TSV, .tab and .psv files preview in Quick Look with an Export button. macOS keeps .csv files on its own Quick Look preview, so for those Gander has a Finder action and its own window.

In Finder, Control-click a CSV file and choose Convert to Excel with Gander, under Quick Actions or Services
Or open it with Gander: a window with up to 200,000 rows that reloads as the file changes, and Export to Excel (⌘E)
In the workbook, numbers, percentages and dates are values, codes such as 007 and postcodes stay as written, and the header is bold and frozen, with filter buttons
A Convert to Excel action for Shortcuts

Read the guide →

daily_forecast.tsv as a grid of 7 columns and 24 rows: dates, cities, station codes such as 08535, highs, lows, rain chance and conditions, with the numbers right-aligned.

Jupyter notebooks, outputs included

.ipynb files open the way the notebook reads: Markdown cells, code coloured in the kernel’s language, and what each cell printed: text, pandas tables, charts and errors with their traceback. Charts are drawn right inside Quick Look, with no Jupyter or Python needed. The Script tab shows all the code as one script, with the Markdown cells as comments.

Read the guide →

forecast_accuracy.ipynb: a Forecast accuracy heading, a Python cell that reads daily_forecast.tsv with pandas, and its table of dates, cities and temperatures.

The same notebook scrolled to a plot cell and its bar chart of the mean forecast error per city.

Mermaid diagrams without a browser

.mmd and .mermaid files open as diagrams, with the source on the next tab. Gander draws flowcharts, sequence, class, state and ER diagrams, XY charts, pie charts, mindmaps, timelines, Gantt charts, user journeys, git graphs, quadrant charts, C4 and requirement diagrams.

Read the guide →

roadmap.mmd as a Gantt chart: the Nimbus 3.0 roadmap with bars for radar tiles and heat index alerts.

branches.mmd as a git graph with main and radar-v2 branches and a v2.4.0 tag.

architecture.mmd as a sequence diagram: User, iOS App, Forecast API and Postgres exchanging requests.

JSON, JSONC and JSON Lines you can actually read

JSON opens instantly, even large files, with Tree and Raw views. JSONC works too, and so do .json files with comments such as tsconfig.json: Raw keeps every comment, and Tree still shows the data. JSON Lines and NDJSON logs show one record per line. Click a line number to expand that record as indented JSON, in the file’s own key order, and click again to fold it.

Read the guide →

forecast.json in the Tree view: city, country and the current conditions as nested keys.

api-requests.jsonl with record 6 expanded as indented JSON, showing an upstream timeout error.

Look inside SQLite databases

.sqlite, .sqlite3 and .db files open read-only, so the database is never modified and no journal files appear beside it. Structure lists every table’s columns, types, keys and indexes. Content shows the rows, table by table, up to the first 1,000 of each.

Read the guide →

nimbus.sqlite on the Structure tab: the api_keys and cities tables with column types, primary keys and NOT NULL flags.

nimbus.sqlite on the Content tab: the cities table with 12 rows of names, countries, latitudes and longitudes.

Every SQL query, neatly aligned

.sql files open Formatted: the keywords are right-aligned in one column, so joins, conditions, CTEs and subqueries read at a glance. Only spacing and keyword case change, and Raw shows the file as written. Anything Gander can’t lay out safely, such as procedures, dbt {% %} blocks and psql scripts, is shown as written. Both views are syntax-coloured, line numbers are one click away, and Finder thumbnails show the formatted query.

Read the guide →

weekly_report.sql on the Raw tab in Dark Mode: the query as written, in lowercase, run together on a few long lines.

weekly_report.sql on the Formatted tab in Dark Mode: SELECT, FROM, JOIN, WHERE, GROUP BY and ORDER BY right-aligned in one column, with a CASE expression, a window function and subqueries laid out beneath.

Logs that open at the newest line

.log files open scrolled to the end, where the latest entries are. Timestamps are dimmed and levels coloured: errors red, warnings yellow, info blue and debug grey, and JSON lines are coloured as JSON. Warnings & errors filters the file down to those entries, stack traces included, with the file’s own line numbers. A large log shows its last 4 MB.

Read the guide →

api.log on All, scrolled to the newest requests, with a yellow WARN for a slow request and a red ERROR from the push service.

api.log on Warnings & errors in Dark Mode: three warnings and three errors, one with its Python traceback underneath.

Secrets stay hidden until you choose

Environment files open with every value masked. Keys stay visible, and likely secrets such as passwords, tokens, API keys and private keys are marked SECRET. Values appear only when you choose Show values, and copying from the hidden view never copies a real value.

Read the guide →

.env.production with Show values on: plain values such as the port and log level next to flagged secrets.

.env.production in the default Hidden view: every value masked, with keys like STRIPE_API_KEY marked SECRET.

Code in 30 languages, config, XML and the rest

YAML, TOML, .cfg and .config files open as typed, colour-coded structures, and package.json gets an overview of its name, version, scripts and dependencies. Code in 30 languages is syntax-highlighted: Swift, Python, JavaScript, TypeScript, Go, Rust, Java, Kotlin, C, C++, Objective-C, C#, Ruby, PHP, CSS and Sass, Lua, Perl, Dart, Scala, PowerShell, shell scripts, Terraform (.tf, .tfvars, .hcl), Dockerfiles, Makefiles and more. TypeScript .ts files show their code even though macOS takes .ts for video, and real .ts videos still play. Diffs and patches show removed lines in red and added lines in green. Code opens clean, line numbers are one click away, and they stay out of anything you copy. XML opens with Tree and Raw views, and property lists such as Info.plist and .entitlements show every key with its type and value, binary ones included. ZIP, XIP, tar and .tar.gz archives list their contents without extracting, GZIP files show their text, and MIDI files play. Text, code and data files up to 1 MB open whole.

main.tf with Terraform syntax highlighting: a provider block, a variable and two Cloudflare resources.

package.json overview: the nimbus-dashboard name, version 2.4.0 and its scripts.

nimbus-2.4.0.zip listing the files inside the archive.

Real thumbnails in Finder

In icon, gallery and column view, Finder shows a page of the file itself: rendered Markdown, coloured JSON, YAML, XML, SQL and code, TSV tables, notebooks, the end of a log, Mermaid sources and archive contents. Thumbnails of .env files show keys only, never values.

README.md
forecast.json
architecture.mmd
docker-compose.yml
nimbus-2.4.0.zip
forecast_service.py
package.json
Cargo.toml
daily_forecast.tsv
forecast_accuracy.ipynb
api.log
roadmap.mmd

Nothing leaves your Mac

Gander reads only the files you preview or export, and saves an export only where you choose. It has no account, no analytics and no networking code, and its extensions run in Apple’s App Sandbox without network access. The App Store privacy label is Data Not Collected.

Read the privacy policy

Runs 100% on your Mac
No account, no subscription
Nothing is uploaded

Set up in under a minute

Install Gander from the Mac App Store.
Open Gander once. Its window shows whether Quick Look is using it, and lets you choose which file types and Markdown extras it handles.
In Finder, select a file and press Space.

Still seeing the standard preview? Turn on Gander in System Settings › General › Login Items & Extensions › Quick Look. The Gander window has a button that opens that page.

Supported file types

Select any of these in Finder and press Space. The last column says whether Finder also shows a Gander thumbnail.

Kind	Extensions	What you see	Finder thumbnail
Markdown	`.md` `.markdown` `.mdown` `.markdn`	Rendered GitHub-flavoured Markdown with Mermaid, math, footnotes, alerts and emoji, plus the Raw source; export to PDF, Word, RTF or HTML	Yes
Mermaid	`.mmd` `.mermaid`	The diagram, plus the source	Yes
JSON and JSONC	`.json` `.jsonc`	Tree and Raw views, fast even for large files; comments are kept	Yes
JSON Lines	`.jsonl` `.ndjson`	One record per line; click a line number to expand it	Yes
package.json	`package.json`	Name, version, scripts and dependencies	Yes
YAML	`.yaml` `.yml`	A typed, colour-coded structure	Yes
TOML	`.toml`	A typed, colour-coded structure	Yes
Config files	`.cfg` `.config`	A typed, colour-coded structure	Yes
XML and property lists	`.xml` `.xsd` `.xsl` `.xslt` `.wsdl` `.rss` `.atom` `.plist` `.entitlements` `.xcprivacy`	Tree and Raw views; property lists by key, type and value, binary ones included	Yes
CSV and TSV	`.csv` `.tsv` `.tab` `.psv`	A spreadsheet grid with Export to Excel (.xlsx); TSV, .tab and .psv in Quick Look, CSV in the Gander window	Yes, except CSV
Jupyter notebooks	`.ipynb`	Markdown, code, outputs, tables, charts and errors, plus the code as one script	Yes
SQLite	`.sqlite` `.sqlite3` `.db`	Read-only Structure and Content tabs, up to 1,000 rows per table	No
SQL	`.sql`	Formatted, with the keywords lined up in one column, or Raw as written; only spacing and keyword case change	Yes
Log files	`.log`	Opens at the newest line, levels coloured, with a Warnings & errors filter	Yes
Environment files	`.env` `.env.` `.env`	Keys with values hidden until you choose Show values	Yes, keys only
Source code	`.swift` `.py` `.js` `.mjs` `.cjs` `.jsx` `.ts` `.tsx` `.go` `.rs` `.java` `.kt` `.kts` `.c` `.h` `.cpp` `.hpp` `.m` `.mm` `.cs` `.rb` `.php` `.css` `.scss` `.sass` `.less` `.lua` `.pl` `.dart` `.scala` `.groovy` `.gradle` `.r` `.ps1` `.proto` `.graphql` `.sh` `.bash` `.zsh` `.fish` `.mk` `Dockerfile` `Makefile` `Gemfile`	30 languages with syntax highlighting, from Swift, TypeScript, Go and Rust to Dockerfiles and Makefiles; line numbers on request	Yes
Diffs and patches	`.diff` `.patch`	Removed lines in red, added lines in green	Yes
Terraform	`.tf` `.tfvars` `.hcl` `.tfstate`	Highlighted blocks, strings and comments; .tfstate opens as JSON	Yes
Plain text	`.txt` `.text` `.ini`, dotfiles, files with no extension	The text, read safely; binary files are left to macOS	Yes
Archives	`.zip` `.xip` `.tar` `.tgz` `.tar.gz`	The list of files inside, without extracting	Yes, except XIP
GZIP	`.gz` `.gzip`	The decompressed text, up to 1 MB	No
Folders	any folder	The list of items inside	No
MIDI	`.mid` `.midi` `.smf` `.kar`	Play, pause and scrub	No

Questions and answers

What is Gander?

Gander is a Quick Look extension for macOS, made by 65FN LLC. When you select a file in Finder and press Space, Gander draws a rich preview for developer files such as Markdown, Mermaid diagrams, JSON, CSV, SQL, SQLite databases, Jupyter notebooks, logs and .env files. It also draws Finder thumbnails for most of them, exports Markdown to PDF, Word, RTF and HTML, and turns CSV files into Excel workbooks.

Which Macs does Gander run on?

Any Mac with macOS 15 or later.

How much does Gander cost?

Free on the Mac App Store. There are no in-app purchases, no subscription and no account.

Does Gander upload or collect my files?

No. Gander has no networking code and collects no data. Previews are drawn on your Mac, and the App Store privacy label is Data Not Collected.

Does previewing an SQLite database change it?

No. Gander opens databases read-only and immutable, so it never writes to the file or creates -wal, -shm or journal files beside it. Rows that exist only in an uncommitted -wal file aren’t shown, and the preview says so.

Does Gander change my SQL files?

No. Gander never writes to the file. The Formatted view lays the query out on screen, changing only spacing and keyword case, and Raw shows the file as written. Anything it can’t lay out safely, such as procedures, dbt {% %} blocks and psql scripts, is shown as written.

Will Gander show the secrets in my .env files?

Only when you ask. Every value is hidden when the preview opens; keys stay visible, and likely secrets are marked SECRET. Choose Show values to reveal them. Finder thumbnails of .env files show keys only.

Can Gander draw Mermaid diagrams inside Markdown?

Yes. A fenced code block marked mermaid is drawn as a diagram inside the rendered page, and .mmd or .mermaid files open as diagrams on their own.

Can Gander export Markdown to PDF or Word?

Yes, and it’s free. In a Markdown preview, press Export next to the copy button, choose PDF, Word (.docx), RTF or HTML, the paper size and page numbers, and save. Or open the file in Gander and choose File › Export (⌘E for PDF); its window shows the whole document and reloads as you edit. Diagrams, tables, math, footnotes and pictures from your Mac come along, and Shortcuts has an Export Markdown action.

Can Gander turn a CSV file into an Excel workbook?

Yes, and it’s free. In Finder, Control-click a CSV or TSV file and choose Convert to Excel with Gander, under Quick Actions or Services. Or open the file with Gander and choose File › Export › Excel Workbook (⌘E); a TSV preview in Quick Look has an Export button too. Numbers, percentages and dates become values, codes such as 007 and postcodes stay as written, and the header row is bold and frozen, with filter buttons. Shortcuts has a Convert to Excel action.

Why does a CSV file still show Apple’s preview?

macOS always previews .csv files with its own viewer, and doesn’t let other apps take that over. TSV, .tab and .psv files get Gander’s preview. To see a CSV file in Gander’s table, Control-click it and choose Open With › Gander, or convert it to Excel from Finder.

I pressed Space and still see the standard preview. What now?

Open Gander once, then go to System Settings › General › Login Items & Extensions › Quick Look and make sure Gander is turned on. If another app previews the same file type, turn that one off. Then select the file in Finder and press Space again.

Why don’t SQLite files get a Gander thumbnail?

macOS doesn’t let third-party thumbnail extensions handle SQLite files, so Finder keeps its own icon. Pressing Space still opens the full Gander preview.

Which languages is Gander in?

English, Spanish, German, French, Japanese, Simplified Chinese and Brazilian Portuguese. Gander follows your Mac’s language.

Can I turn some previews off?

Yes. The Gander window has a switch for each file category and for each Markdown extra: math, footnotes, GitHub alerts and emoji. Switch a category off and Gander stops handling that type.

Why do images in my Markdown show as text?

Quick Look previews can’t load images, so Gander shows each one as a picture icon and its alt text. The Gander window and exports include pictures stored on your Mac; Gander asks for access to their folder. Images on the web are never downloaded.

Gander at a glance

Name: Gander (on the App Store: Gander: Quick Look Preview)
What it is: A Quick Look preview and Finder thumbnail extension for macOS, with Markdown export and CSV to Excel
Developer: 65FN LLC
Requires: macOS 15 or later
Price: Free
Where to get it: Mac App Store
Privacy: Data Not Collected; no network access
Category: Developer Tools
File types: 97 file extensions, plus dotfiles, extensionless files and folders
Languages: English, Spanish, German, French, Japanese, Simplified Chinese and Brazilian Portuguese
Version: 1.4

Press Space — take a gander

See it in 30 seconds

A viewer for each file in your project

Markdown, rendered the way GitHub shows it

Export Markdown to PDF, Word, RTF or HTML

CSV and TSV as a real table, then on to Excel

Jupyter notebooks, outputs included

Mermaid diagrams without a browser

JSON, JSONC and JSON Lines you can actually read

Look inside SQLite databases

Every SQL query, neatly aligned

Logs that open at the newest line

Secrets stay hidden until you choose

Code in 30 languages, config, XML and the rest

Real thumbnails in Finder

Nothing leaves your Mac

Set up in under a minute

Supported file types

Questions and answers

What is Gander?

Which Macs does Gander run on?

How much does Gander cost?

Does Gander upload or collect my files?

Does previewing an SQLite database change it?

Does Gander change my SQL files?

Will Gander show the secrets in my .env files?

Can Gander draw Mermaid diagrams inside Markdown?

Can Gander export Markdown to PDF or Word?

Can Gander turn a CSV file into an Excel workbook?

Why does a CSV file still show Apple’s preview?

I pressed Space and still see the standard preview. What now?

Why don’t SQLite files get a Gander thumbnail?

Which languages is Gander in?

Can I turn some previews off?

Why do images in my Markdown show as text?

Gander at a glance

Press `Space` — take a gander