Joiner for DJI

You flew for 22 minutes and the drone’s card has three videos for it, each with its own .SRT file. A DJI drone starts a new file every time the video reaches about 4 GB. You want the one flight you recorded, in one video.

$20 including tax, paid once.

Joiner for DJI is a Mac app that puts the parts back together. Plug in the card and each flight it finds shows up as one row. Tick it, click Join, and one video lands on your Mac, with one .SRT file that still lines up with it. The picture and the sound are copied exactly as the drone recorded them, so nothing loses quality.

What’s on a drone’s card

A DJI drone names each file after the moment it started and a counter. The parts of one flight are just files with the next numbers, and nothing in their names says they belong together.

File on the card	What it is
DJI_20260712101530_0007_D.MP4	Part 1 of the flight, started at 10:15:30
DJI_20260712102508_0008_D.MP4	Part 2, started where part 1 ended
DJI_20260712103446_0009_D.MP4	Part 3, the last one
DJI_20260712101530_0007_D.SRT	The flight data of part 1: position, height and camera settings, line by line
DJI_20260712101530_0007_D.LRF	The small, low-quality copy of part 1, for the DJI phone app
DJI_20260712101530_0007_D joined.MP4	What you get on your Mac: the flight in one video
DJI_20260712101530_0007_D joined.SRT	And its flight data in one file

Older drones name their files DJI_0001.MP4, DJI_0002.MP4, and the app reads those too.

It asks before it joins a guess

Since the drone doesn’t mark which files go together, Joiner for DJI works it out. It looks at the numbers, the video settings and the times: when one file ends exactly where the next one starts, they look like one flight.

That’s still a guess, so the app shows it and waits for you. Under the row it explains why, like “These 3 files look like one recording: each one starts where the one before it ends. Tick the box if they belong together.” It never joins a guess on its own.

Click Show the 3 files to see the parts, or click the row to watch the first one in a small panel in the corner of the window.

The flight data, lined up

Each part has its own .SRT file, with the drone’s position, height and camera settings for every moment of that part. Its times start from zero, so the .SRT of part 2 starts at zero too.

Joiner for DJI merges them into one file and shifts every line of part 2 and part 3 by the length of the parts before. The joined .SRT lines up with the joined video from the first second to the last, and it’s checked like the video. The row then says “The .SRT subtitles were joined and checked too”, with the file’s name.

If you rename the joined video with Rename…, its .SRT follows.

Straight from the card

The app reads the parts where they are, on the card, and saves the joined video on your Mac. Nothing is copied first, so there’s no second set of files to clean up.

Here’s how it goes:

1. Put the card in your Mac. The start screen gets a button with the card’s name, like Scan NO NAME.
2. Read the note under each flight and tick the ones whose parts belong together.
3. The joined videos go to your Movies folder unless you click Change…. Click Join.

The first time, macOS asks whether Joiner for DJI can read the card. Click Allow.

Flights you already copied to your Mac work the same way. Drop the folder on the window, or click Downloads, Desktop or Movies.

Nothing loses quality

Most apps that join videos rebuild every frame. That takes a long time, and the picture comes out a little worse than it went in.

Joiner for DJI doesn’t touch the frames. It puts the parts one after the other, as they are. Before it says it’s done, it compares the joined video with the parts, piece by piece, then asks macOS to open it. If anything is off, the joined file is thrown away and your parts are where they were.

It never replaces a file either. When a name is taken, it offers the next free one, like DJI_20260712131010_0015_D joined 2.MP4.

Short clips too

The videos your drone didn’t split are listed under the flights, oldest first. Tick two or more to make one video out of them. They’re named after the days they were recorded, like 2026-10-08 to 2026-10-15.MP4. Drag a row to change the order.

Then free the card, small files included

Next to every video, a DJI drone saves an .LRF file, a low-quality copy for its phone app. Once the video is gone it’s clutter, and deleting the videos in the Finder leaves it behind.

After a join that says Joined and checked, click Move Originals to Trash…. The parts go with their .SRT files, since those are now in the joined one. The confirmation has a box, ticked for you, that takes the .LRF files of those videos with them.

Only the .LRF files of the videos being removed go, matched by name. Untick the box to keep them.

Nothing happens until you confirm, and Keep Originals is the default button, so pressing Return never removes anything.

On a memory card, the Trash is on the card. macOS keeps a card’s trashed files in a hidden folder on the card itself, so they keep taking up space until you empty the Trash. The confirmation says so, and adds Delete Now, which frees the space right away and can’t be undone.

Right before it removes anything, the app looks at the joined video once more. If you moved it or edited it in the meantime, the parts stay and the app tells you why.

Good to know

Joiner for DJI is my own app. It’s not made by, affiliated with or endorsed by DJI.

The app checks every join before it offers to remove anything, but I’m not responsible for lost videos. Keep a backup of footage you care about, and play the joined video before you delete the parts.

It doesn’t trim or convert videos.

The videos you join have to be recorded with the same settings, like the same picture size. Making different ones fit would mean rebuilding every frame, so files with different settings are never offered as one flight, and when you tick clips that don’t match, the app says which one is the odd one out.

It reads MP4, MOV and AVI videos. Videos from another camera in the same folder are listed too, and you can join them the same way.

The card sets the speed. Expect about the time it takes to read the parts twice: once to join them and once to check them.

Buy Joiner for DJI and get started

Joiner for DJI costs $20 including tax, paid once. There’s no subscription.

After buying, your receipt has the app and a license key. Unzip the app and drag Joiner for DJI to your Applications folder. It runs on macOS 14 Sonoma or later, on Apple silicon and Intel Macs. It’s signed with my Apple Developer ID and checked by Apple, so it opens like any other app you download.

Enter the license key in Joiner for DJI → License… to get updates automatically. A key works on 3 Macs. Once a day, Joiner for DJI checks for a new version, shows what’s new, and installs it with Install and Relaunch. Your receipt always has the latest version, too.