# Open log files at the newest line, with errors in red

> Preview .log files in Finder: they open at the end, with levels coloured and a Warnings & errors filter that keeps each stack trace with its error.

When you open a log, you want the end of it. Gander opens `.log` files scrolled to the newest line, colours each level and filters the file down to warnings and errors, stack traces included, with one press of Space in Finder.

![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.](https://ganderfinder.com/img/features/log-all-2x.webp)
![api.log on Warnings & errors in Dark Mode: three warnings and three errors, one with its Python traceback underneath.](https://ganderfinder.com/img/features/log-warnings-2x.webp)

## How to do it

1. Install Gander from the Mac App Store and open it once.
2. Select a `.log` file in Finder and press Space.
3. Read from the bottom, or switch from **All** to **Warnings & errors**.

## Readable at a glance

Each line is coloured by what it is:

- Errors in red, warnings in yellow, info in blue and debug in grey
- Timestamps dimmed, in ISO, syslog, Apache and other common formats
- JSON log lines coloured as JSON, with the level taken from fields such as `level` or `severity`
- Stack traces, Python tracebacks and `Caused by` lines kept with the entry above them

## Warnings & errors

One switch filters the log to its warnings and errors, each with its stack trace, and keeps the file’s own line numbers so you can find them again. A summary counts them, for example “12 errors · 3 warnings”.

## Large logs

For a large log, Gander reads the last 4 MB, the part you usually need, and says so. Finder thumbnails show the last lines, coloured, so a failing run stands out from its icon.

## Questions

### Why does the log open at the bottom?

The newest entries are at the end of a log, so Gander starts there. Scroll up for older lines.

### Which log formats does Gander recognise?

Text logs with level words such as ERROR, WARN, INFO and DEBUG (in capitals, in brackets or after `level=`), the common timestamp formats, and JSON lines from loggers such as pino and bunyan.

### Does it work with very large logs?

Yes. Gander reads the last 4 MB of the file, so even huge logs open quickly, and the preview says how much it shows.

## More guides

- [Preview Markdown in Finder, rendered the way GitHub shows it](https://ganderfinder.com/markdown-quick-look)
- [View Mermaid diagrams on your Mac without a browser](https://ganderfinder.com/mermaid-viewer)
- [Turn Markdown into a PDF or a Word document, right from Finder](https://ganderfinder.com/markdown-to-pdf-word)
- [Convert CSV to Excel on your Mac, straight from Finder](https://ganderfinder.com/csv-to-excel)
- [Read Jupyter notebooks on your Mac without starting Jupyter](https://ganderfinder.com/jupyter-notebook-viewer)
- [A fast JSON viewer in Finder, for JSONC and JSON Lines too](https://ganderfinder.com/json-viewer)
- [Look inside an SQLite database from Finder](https://ganderfinder.com/sqlite-viewer)
- [Read any SQL query neatly laid out, without changing the file](https://ganderfinder.com/sql-formatter)
- [Check a .env file without putting secrets on screen](https://ganderfinder.com/env-file-viewer)

Gander is free on the Mac App Store, with no in-app purchases, no subscription and no account, and nothing you preview leaves your Mac. https://apps.apple.com/app/id6817038818

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