Frequently asked questions

Short answers. Each links to the page with the full story.

Safety

Is it safe? Will it delete something I need? Trawler never removes anything on its own. It finds files and shows them to you; you tick what goes, and nothing happens until you press the button on the last step of the processing screen. The default action is Archive to ZIP, which frees the space and keeps the files inside the archive it writes. → What can be undone

Can I undo it? Depends what you chose. Archive to ZIP and Move to another location are reversible from inside Trawler — archiving needs the archive you kept, and a move back needs both the moved files and the record Trawler left in the destination folder. Move to Recycle Bin is reversible from the Windows Recycle Bin. Delete permanently and Replace with hardlink are not. → What can be undone

Will it touch Windows or my installed programs? Not unless you ask it to. Windows and Program Files are on the Protected paths list out of the box, and folders on that list are skipped during scans entirely — so they never appear in results, and nothing there can be ticked. The list is yours to change: remove an entry and the next scan looks there like anywhere else. → Settings

What if it's wrong about two files being duplicates? On the Duplicates tab, files are only grouped after every byte of both has been compared, so a group from a Find duplicates scan is an exact copy as a matter of fact. If Verify exact copies is showing on that tab, the results came from sampling rather than a full read — run it before treating a group as identical. Similar files is different again — those are advisory, nothing is pre-ticked, and you decide every one. → Index files, or find duplicates

Results

Why didn't it find my OneDrive / Google Drive / Dropbox files? Cloud files that aren't downloaded to your PC are skipped by default, so scanning doesn't quietly pull gigabytes down and fill your drive. There's a setting to include them. → Why didn't it find my OneDrive files?

It found fewer files than I expected. Most often one of three things: a filter narrower than you meant, a protected folder being skipped entirely, or cloud-only files. → What kind of files · Troubleshooting

I picked Music, but the scan found photos and videos too. Those categories are ticked under Include similar items on Home, so the scan takes their files in for similar matching. The What kind of files? step marks each added row Also scanned. Untick them on Home to keep the scan to Music. → What kind of files · Similar files

Can I search the results for one name or one file type? Yes. Filter, in Explore → Filter results, takes a word, a .type, or both. A dot means file type and anything else means "appears in the path", so .pdf finds PDFs and invoice finds anything with invoice in its path. It narrows what you see and nothing else — your ticks are untouched. → Filtering your results

I filtered a tab and now it's empty. Did I lose the results? No. No matching files means the filter matched nothing, and the scan results are all still there. Click Clear filter, or click the chip beside the funnel to drop one half of it. → Filtering your results

Do images from my iPhone match? Yes. HEIC and HEIF are matched like any other image, and a HEIC groups with a JPEG of the same shot. They rely on the HEIF support built into Windows; if this PC does not have it, Trawler says so once with a count, and installing HEIF Image Extensions from the Microsoft Store fixes it. → Similar images

Two photos look identical. How do I tell which one to keep? Put them one on top of the other instead of side by side. The compare pane has Wipe, Blend and Flip buttons: Wipe drags a divider across the pair, Blend fades one into the other, and Flip switches between them every 0.6 seconds, so anything that moves is a difference. If the two do not sit squarely on top of each other, turn Sync off and drag the second picture into line first. → Comparing two images

I cropped a photo and Trawler doesn't group it with the original. Why not? Trawler compares the whole picture at once, so trimming even a narrow border shifts everything it looks at. The two pictures stop resembling each other and the copy drops out of the group. Lowering the Similarity slider does not bring it back — it finds unrelated pictures long before it finds the crop. Cropped copies are a job for your eyes. → Similar images

What's the difference between Duplicates and Similar files? Duplicates are the same file twice — matched on their contents, and proven identical by a Find duplicates scan. Similar files merely resemble each other: the same image at two sizes, the same song from two albums, two drafts of one document. Different question, different answer, and only the first is safe to act on in bulk. → Similar files overview

A file's column in the Details panel says "FFmpeg required", or "Cloud file, not downloaded". Why? The first is a video Trawler can only read with FFmpeg, and it can't find ffmpeg.exe and ffprobe.exe. MP4, MOV, M4V, AVI, WMV, MKV and WebM files show their main properties without them. The second is a file that lives only in the cloud, which Trawler leaves alone unless Include cloud-only files by default is on in Settings. The other messages are explained in the same place. → The Details panel

The Videos tab says it needs FFmpeg. Video matching needs two free programs — ffmpeg.exe and ffprobe.exe — that don't ship with Trawler. There's a Download FFmpeg link on that screen, and you can point Trawler straight at them afterwards. → Similar video

Speed and size

Why is the scan slow? Usually the number of files, a network location, or the duplicate check itself — Find duplicates reads every byte of every candidate, and Index files reads none of them. → Index files, or find duplicates · Big scans

Can I use my PC while it runs? Yes. Long jobs have a Run in background button, and there's a CPU limit in settings if you want Trawler to stay out of your way. → While it's running

Can I stop a scan without losing everything? Yes. Cancelling keeps the work already done — you lose only whatever was in flight when you pressed it. → While it's running

It said the drive ran out of space, or that the scan ran out of memory. Two different messages with two different fixes. Out of disk means freeing space on the drive holding the results. Out of memory means the results will not fit in memory, and the fix is to scan less or switch where results are kept. → Why did the scan stop?

I want to add another drive to a scan I already ran. Does it start over? No, as long as you haven't closed Trawler since. Files that haven't changed keep the work already done, so you pay for the new drive rather than for both. → Big scans

Trawler crashed part-way through a long scan. Do I have to run it all again? No, on the full version. The next launch offers the unfinished scan back — Continue this scan picks it up, Discard throws it away, Not now asks again next time. The free version clears it instead. → Sessions

Organizing what remains

Can I put the files left after cleanup into different folders? Yes. Organize → Organize files has its own checks and assignment queue. Choose Current scan for files included in your open scan, or Free-form to organize files without a scan. Both need the full version. → Organizing your files

Does Undo put moved files back? In Organize, Undo changes planning edits only. It does not reverse completed moves, ZIP additions, or recycling. Cancel stops further work and keeps completed actions. → Organizing your files

The free version

What can't I do without paying? You can scan anything, run every match, see every total, and tick everything you would remove. What's blocked is the moment files change — archiving, recycling, deleting, moving, hardlinking — plus Organize, saving and reopening sessions, exporting to CSV, scanning a network location, and keeping results on disk instead of in memory. → Free and full versions

Can the free version scan my whole C: drive? Yes. Local drives — the disks in the machine and anything plugged in — can be scanned whole on any version, and the totals are the real ones. The free version keeps the results in memory, so a very large drive can produce more results than memory can hold and the scan then stops before it finishes; the full version saves them to disk instead. Network locations are the one target the free version refuses. → Free and full versions

Why can I only see ten groups? The free version shows the first ten in Duplicates and in each Similar tab. The totals aren't capped — the group count and the reclaimable figure are always the real numbers for the whole scan, so you can see exactly what the full version would save you before deciding. → Free and full versions

I paid — how do I check it worked? Settings → About. The License row reads "Full version" once the unlock is yours. If it reads "Couldn't check", Trawler could not reach the Store — that is not the same as no purchase, so get back online and start Trawler again before worrying. → Settings

Why is a button greyed out? Usually one of four reasons: another job is already running, the action needs the full version, Replace with hardlink hasn't been enabled in settings, or nothing is ticked yet. → Why can't I click a button?

Files and formats

I can't open the archive Trawler made. Three of the four compression choices produce an ordinary .zip. The fourth — "Smallest file, one format" — produces a Solid archive that Windows can't open by double-clicking. Use 7-Zip or WinRAR, or open it in Trawler's own Restore, which reads both. To look inside one without restoring anything, open it in Trawler's folder tree. → Restoring from an archive · Looking inside an archive

Can I see what's inside a .zip without unpacking it? Yes, and a .7z or one of Trawler's own .tar.zst archives too. Archives show in the folder tree; open one there and the Files tab lists what it holds. Double-click a file to view it. Nothing inside an archive can be ticked, and Trawler never changes it. → Reading results

What is a hardlink, and should I use it? It makes several copies share one set of contents, so you get the space back without losing any of the filenames. The catches: one drive only, editing one edits all of them, and it can't be undone. It's off until you turn it on. → Processing

There are .trawler-tmp files on my drive. Leftovers from a job that was interrupted. Trawler clears them at startup — but only in the folders listed under Default scan roots, so if that list is empty it never runs. → Recovering an interrupted hardlink job

Can I get the results out of Trawler? Yes — Export CSV on the duplicates view and in Scan report. Both need the full version. → Reading results

Getting help

Where are the log files? %LOCALAPPDATA%\trawler\logs\, one per day, kept for seven days. Settings → General → Open logs folder takes you there. → Where the log files are

Something isn't covered here. When something goes wrong explains the Scan report and what each kind of entry means. The Glossary defines the terms as the app uses them.