Guide

How to check whether a transcription app is really uploading your audio

Three tests, from thirty seconds to thorough. None of them requires you to trust the developer — including us.

27 August 2026

Every transcription app says it respects your privacy. The word "secure" appears on all of their websites, including the ones that upload your recordings to a server and keep them.

If you handle interviews with sources, client conversations, patient audio, or anything under a consent agreement, a marketing claim is not good enough. The useful thing about this particular question is that you can check it yourself in about a minute, and you do not have to take anyone's word for it.

Here are three tests, in order of effort.

Test 1: Turn off the internet #

This takes thirty seconds and requires nothing you do not already have.

1. Turn on Airplane Mode, or just switch off Wi-Fi and unplug Ethernet.
2. Open the app.
3. Transcribe a real file.

That is the whole test. An app that cannot reach a server cannot upload to one. If a transcript comes back, the work happened on your machine — there is no third possibility.

If instead you get a spinner, an error, or a message about checking your connection, you have your answer too.

The reason this test is so useful is that it cannot be faked. A developer can write anything on a website; nobody can transcribe your audio on a server you are not connected to.

Test 2: Watch the bytes in Activity Monitor #

Airplane Mode proves an app can work offline. It does not prove the app is not also sending a copy when you are online. For that, watch the traffic.

Activity Monitor is already on your Mac.

1. Open Activity Monitor (Command-Space, type "Activity Monitor").
2. Click the Network tab.
3. Click the Sent Bytes column to sort by it.
4. Find the transcription app in the list, and note the number.
5. Transcribe a large file — the bigger the better, a 50 MB recording is ideal.
6. Watch the number.

What you are looking for is whether Sent Bytes grows in proportion to the size of your file. Uploading a 50 MB recording means sending 50 MB. That is not subtle and it cannot be hidden — it will be plainly visible in that column.

A few kilobytes here and there is normal for almost any app: checking for updates, validating a licence, fetching prices. Fifty megabytes is your recording leaving the building.

Test 3: See every connection by name #

If you want to know exactly what an app is talking to rather than just how much, you need a network monitor.

• LuLu is free and open source, from Objective-See.
• Little Snitch is paid and more detailed.

Either one will prompt you, or log an entry, every time an app tries to make an outbound connection, and tell you the hostname it is reaching for. Install one, then transcribe something and watch what appears.

This is the test that distinguishes "this app phones home about licensing" from "this app is sending my interview to a server in another country."

What you will see with Offline Transcription #

Being specific here, because a vague answer would defeat the point of the article.

Offline Transcription does make network connections. It talks to RevenueCat, which handles purchases, to check whether you have Pro and to fetch current prices. You will see those connections at launch and when the purchase screen opens. That is the only thing in the app that uses the network — there is no analytics SDK and no other server involved.

It never sends audio. Transcription runs through Whisper on your own processor. Regardless of whether you transcribe a 10-second voice memo or a three-hour recording, the bytes sent do not change, because nothing about your file is transmitted.

The clearest demonstration is Test 1. Put the Mac in Airplane Mode and transcribe a two-hour interview. It works, because the model is inside the app and the processing happens on your chip.

We would rather tell you about the RevenueCat connections than have you find them yourself and wonder what else we left out.

What these tests do not prove #

Worth being clear about the limits.

None of this tells you what an app does with a file after it has been uploaded, if it uploads one. It does not verify what happens on someone else's server, which is the whole difficulty with cloud services — you are being asked to trust a retention policy you cannot inspect.

It also does not tell you anything about an app that batches uploads for later. If you are being properly careful, run Test 2 over a longer session rather than a single file.

And Airplane Mode does not prove an app never uses the network for anything, only that it does not need the network to do the transcription. Those are different claims, and the second is the one that matters for your recordings.

The short version #

An app that transcribes in Airplane Mode is processing your audio locally. There is no way around that, and no marketing claim needed in either direction.

If you are choosing a transcription tool for confidential material, run the thirty-second test on each candidate before you decide. It will tell you more than any privacy policy.