Set a Folder, Walk Away
How Watch Folder automation handles your entire conversion pipeline without you in the loop
Most people convert audiobooks one at a time. Open the app, drag in a file, pick the output format, click convert, wait, repeat. That workflow is fine when you're processing one or two files. When you're ripping a full library from physical media, or you have a download folder that fills up regularly, manually repeating those steps for forty files is a serious time sink.
Watch Folder solves this. Point it at a folder, configure what you want done to files that land there, and the Audiobook Converter Pro app handles everything else. A new M4B arrives. The app detects it, converts it according to your settings, and puts the output where you specified. You were doing something else the entire time.
That's the pitch. Here's what's actually happening inside.
What Watch Folder Monitors
A Watch Folder profile ties a specific input folder to a set of conversion settings. You can have multiple profiles, each watching a different folder with different output configurations. A folder for raw library rips going to FLAC. A separate folder for listening copies going to MP3 at 128 kbps. They run independently and don't interfere with each other.
Each profile has two processing modes. Queue Only adds detected files to the conversion queue in the app but waits for you to start the conversion manually. Auto Convert detects the file, queues it, and starts converting without any input from you.
Queue Only is useful when you want to review files before they're processed, or when you want to batch up a set and convert them together at a specific time. Auto Convert is the true hands-off mode.
The Stability Window
One of the less obvious requirements for folder watching is that you can't just convert a file the instant you see it appear. Files take time to write. A large M4B being copied from an external drive or downloaded from the internet exists in a partially-written state for seconds or minutes before it's complete. If the app starts reading it immediately, it reads an incomplete file and either fails or produces a broken output.
Watch Folder waits 10 seconds after detecting a new file before touching it. That stability window gives file writes time to complete before conversion begins. For very large files over slow connections you might see a file sit briefly in a pending state before the app picks it up; that's intentional.
The app also keeps a receipt store for every file it has already processed. If a file appears in a watched folder that the app has seen and handled before, it gets ignored. This prevents reprocessing files that were already converted and prevents duplicates if you run the app multiple times on a folder that already has files in it.
Initial Discovery
The first time a Watch Folder profile becomes active, there's a decision to make about files already in the folder. The Include Existing Once policy discovers those existing files on first activation and processes them. This is the default behavior, useful when you're setting up a profile for a folder that already contains files you want converted.
The New Files Only policy ignores existing files entirely and watches only for files added after the profile was enabled. This is better when the folder already contains files you've already dealt with, or when you only want to process new arrivals going forward.
The initial discovery runs once. On subsequent activations of the same profile, only new arrivals get picked up.
Per-Profile Settings
Each Watch Folder profile can use one of three settings modes.
The first inherits from your global app preferences. Whatever output format, bitrate, and chapter handling you have configured in the main preferences panel, the Watch Folder uses those same settings. Change the global preferences and the Watch Folder picks up the change automatically.
The second uses a named preset. Three built-in presets cover the most common cases: MP3 at 128 kbps split by chapters, AAC at 128 kbps split by chapters, and FLAC at lossless quality split by chapters. Each preset includes auto-rename on output to avoid filename collisions.
The third mode is fully custom per-profile. You set the output format, bitrate, output mode, overwrite policy, and chapter strategy just for that profile. Nothing from the global preferences bleeds in. This is the mode for situations where one folder needs completely different settings from everything else.
What Happens With Markerless Files
Most audiobooks have embedded chapter markers and Watch Folder handles them without any special handling. The app reads the markers, slices the audio accordingly, and produces chapter-split output files.
Files with no embedded markers require a decision about how to proceed. The Watch Folder respects a per-profile policy for these cases. The conservative option queues markerless files for your review rather than processing them automatically. You get a notification and decide what to do with each one yourself.
The more aggressive option runs silence-based chapter inference and converts automatically, but only when the inference confidence score comes back high. Low-confidence detections still get queued for review rather than processed silently. This means the app will not produce weirdly-split output from a file it wasn't confident about and deliver it to your output folder without you knowing.
Profile Health
Watch Folder profiles depend on file system bookmarks to maintain access to the monitored folders across app restarts and macOS permission checks. If a bookmark becomes stale because a drive was disconnected or a folder was moved, the profile shows a health issue rather than silently failing to monitor anything.
The Watch Folder view in the app shows the health status of each profile. Healthy profiles show as active. Profiles with a missing or stale bookmark show an error state with enough information to understand what went wrong. The app does not silently drop files because a profile is broken; it reports the problem and waits.
The Practical Use Case
The workflow this is built for is simple to describe. You have a folder where audiobooks land, whether from a download manager, a CD ripper, or manual transfers from a NAS. You create a Watch Folder profile pointed at that folder with Auto Convert enabled. From that point, new files arriving in the folder get processed automatically and their converted output appears in your designated output location.
You can close the app. Files that arrive while it's closed get picked up the next time the app launches and applicationDidBecomeActive triggers the auto-run scheduler. Nothing gets lost between sessions. Files detected while the app was closed appear in the pending queue when you reopen the app, and processing starts from there.
What It Doesn't Do
Watch Folder does not monitor formats other than M4B. The file picker for the input folder intentionally restricts to M4B files. This is a scoping decision, not an oversight.
Watch Folder also does not upload files anywhere. All processing runs locally on your machine using the bundled FFmpeg binary. The converted output goes to the folder you specified, same machine, no external services involved.
Availability
Watch Folder is a Full Pro feature. The Free tier shows the Watch Folder interface but does not enable the monitoring. Single Pro includes most conversion features but not Watch Folder automation. Full Pro includes everything.
If you're processing a large library or you have an ongoing workflow where new audiobooks arrive regularly, the automation Watch Folder provides saves enough time to be worth it. The first time you come back to a folder full of already-converted files you didn't have to manually process, the math is obvious.
Audiobook Converter Pro is available on the Mac App Store and the Microsoft Store. Try the Free tier first to see how the conversion flow works, then upgrade when Watch Folder becomes useful.
Anoop builds Audiobook Converter Pro on weekends. The Watch Folder system turned out to need more edge case handling than the initial design suggested, mostly around file stability windows and bookmark lifecycle. That's usually how it goes.
