Open, filter and compare huge log files

There is no size limit that comes from the app. It never reads the file - it maps it, indexes line positions in the background, and draws only the lines on screen. A two-gigabyte log opens in milliseconds and uses about as much memory as an empty window.

Yes, the same way as any other file: choose it with Command-O - Command-Shift-G takes the panel straight to a typed path - or drop it on the window. The sandbox only rules out the app browsing system folders uninvited; hand it the file once and it reopens from Recents from then on. A few system logs are readable only by root, and no App Store app can change that.

Yes. Copy the text, open an empty Log Viewer window and press Command-V. It is opened as a temporary pasted log, not added to Recents, and its private backing file is removed when you close or replace it. For a large or live log, open the original file instead.

It should not, as a rule - opening a file records a grant that survives relaunching. The grant can still die: a file replaced wholesale, a disk remounted, a permission macOS declined to record. When it does, clicking the entry opens a panel already pointed at the right folder, so handing the file back is one click - and the new grant sticks.

Find jumps between matches while the rest of the file stays where it is. Filter collapses the file to the matching lines only, keeping their original line numbers and marking every stretch it hid. Filter is usually what you actually wanted.

Yes. Once the filter has finished, choose Export to save the matching lines - and any context currently shown - as a new file. The original log is never changed.

Yes. In Settings > Redaction, turn on local redaction and adjust the ordered rules for tokens, email addresses, and IP addresses. Regular Copy and filtered Export replace matching values, while the open log and original file remain unchanged. To export every line safely, filter with the regular expression .* and export the redacted view. Read the redaction guide.

Yes. Choose File > Open Beside… and select the other log. It opens in its own window beside the current one, so its filter, search and Follow state stay independent. When there is room, the windows are arranged side by side; tabs can still be merged or moved into their own window from the Window menu.

Yes. Turn on Follow and new lines are indexed as they arrive. If you scroll away it stops moving and shows a count of what has arrived since, so you can go back when you are ready. Truncation, rotation and deletion are all handled without losing what you were reading.

Yes. Settings has an ordered list of rules, each a pattern, a text color, and optionally a tint for the whole line it matches. Add to them, reorder them, edit them or reset them. The first rule that matches wins, so the order is the behavior.

They are read, not printed. Log Viewer paints what they asked for and takes the codes out of the text, which on a docker compose log is most of the width of the window back. Settings can also drop them entirely, or leave them visible if what you are debugging is the codes themselves. Your own highlight rules win over what the log asked for, and copying a line gives you what you could see rather than the escape codes you could not.

Not yet. A .gz file cannot be mapped or seeked, so supporting it would mean decompressing to a temporary file first - a different experience from the one this app is built around. It is the one feature on the list with a real case for a future version.

No. The app has no networking code at all, no accounts and no analytics. There is nowhere for a log to go.