How to Add Soft & Hard Subtitles to MP4 files

MP4 is a video file that fully supports subtitles.

But should you use soft subtitles or hardcode them into the video? And how to implement them ?

In this guide, we’ll walk you through everything you need to know to add subtitle tracks to your MP4.

Can You Add Soft or Hard Subtitles to MP4 Videos?

Yes, you absolutely can.

MP4 is one of the most flexible video formats out there. It supports both soft and hard subtitles, depending on how you want to use them.

Let’s break down what each one means for your MP4 video.

Soft Subtitles

Soft subtitles are stored as a file track inside your MP4. Viewers can turn them on or off whenever they want.

You’ve probably seen this when watching YouTube or Netflix. You click the "CC" button to choose the subtitle language — that’s soft subtitles at work.

These subtitles don’t change your original video. They’re easy to edit, update, or translate into other languages. And they keep your video looking clean when not activated.

Hard Subtitles

Hard subtitles are encoded into the picture of your MP4 file. They’re always visible because they’re part of the video image itself.

You can’t turn them off, and you can’t edit them once exported. But they guarantee your message is always on-screen — no matter where the video is watched.

How to Add Soft Subtitles to MP4

To add soft subtitles, you’ll need two things:

1. Your MP4 video file
2. A subtitle file — usually in .SRT or .VTT format

These subtitle files contain the dialogue text, along with timecodes to sync with your video. You can write them by hand, or create them automatically with tools like Checksub.

Option 1: Use VLC Media Player (for viewing only)

If you're just looking to view your MP4 with soft subtitles locally, VLC makes it simple.

• Open VLC and play your MP4 video.
• Go to the top menu: Subtitle > Add Subtitle File…
• Choose your .SRT or .VTT file.
• Your subtitles now display in sync with the video.

This method doesn’t save the subtitles inside the MP4. It’s just for viewing. If you send the video to someone else, you’ll need to include the subtitle file too.

Option 2: Use MKVToolNix to Embed Soft Tracks

Want to actually store the subtitle track inside your MP4 (or MKV)? You’ll need a tool like MKVToolNix.

• Download and open MKVToolNix GUI.
• Drag your MP4 video into the input section.
• Add your .SRT file underneath as a new track.
• Click “Start Multiplexing”.

This process creates a new video file — typically an .MKV — with the subtitle track included. Most modern players can read MKV just like MP4.

Want to stay in MP4 format? Use FFmpeg instead.

Option 3: Use FFmpeg to Add Subtitles to MP4

If you’re comfortable with command-line tools, FFmpeg is powerful and free.

Here’s the basic command to add soft subtitles:

css

CopierModifier

ffmpeg -i video.mp4 -i subs.srt -c copy -c:s mov_text output.mp4


This command takes your MP4 and .SRT, then creates a new MP4 file with the soft subtitles embedded. The mov_text codec is what makes it compatible with MP4.

How to Burn Subtitles into MP4

Sometimes, you want your subtitles to always be visible. No toggling. No separate files.

That’s what burned-in subtitles do. They’re hardcoded into the video itself — like part of the image.

Here’s how you can add them to your MP4.

Option 1: Use HandBrake (Free and Simple)

HandBrake is a free video encoder that lets you burn subtitles easily.

• Download and open HandBrake
• Import your MP4 video
• Go to the “Subtitles” tab
• Click “Import SRT” and select your subtitle file
• Check the box that says “Burn In”
• Hit “Start Encode”

HandBrake will export a new MP4 with your subtitles permanently embedded.

It’s a great tool for quick, clean results — but limited if you need advanced styling.

Option 2: Use FFmpeg for Custom Control

If you want more control, FFmpeg is your best friend. It’s command-line based, but powerful.

To burn in subtitles:

lua

CopierModifier

ffmpeg -i video.mp4 -vf subtitles=subs.srt output.mp4


This command overlays your .SRT file directly onto the video.

Want to customize the look? Convert your .SRT to .ASS format with styles (using a tool like Aegisub), then run:

lua

CopierModifier

ffmpeg -i video.mp4 -vf "ass=subs.ass" output.mp4


This lets you add fonts, colors, sizes, backgrounds, and more.

How to Add Subtitles Automatically to MP4

Checksub makes it easy to subtitle your MP4 automatically — from upload to export.

Here’s how it works:

Step 1: Upload Your MP4

Go to checksub.com and sign into your account. Don’t have one? Signing up is quick — and free to try.

Click “Upload Video”, and choose your MP4 file.

Select the original language of your video. If you want subtitles in other languages, Checksub offers automatic translation in over 267 languages.

Step 2: Edit and Style Your Subtitles

Once uploaded, Checksub’s AI goes to work:

• It transcribes your audio with high accuracy
• It syncs subtitles perfectly with the speech
• It breaks down long sentences into clean, readable chunks

Inside the editor, you can:

• Fix small errors or add speaker names
• Change fonts, sizes, colors, and positions
• Add backgrounds or effects for better readability

You keep control — without doing everything yourself.

Step 3: Export Your Subtitled Video

When you're done, choose how to use your subtitles:

• Export as .SRT or .VTT for soft subtitles
• Download your MP4 with burned-in subtitles — styled and synced
• Or grab both, for flexibility across platforms

You want to generate MP4 subtitles with AI ? Try Checksub for free now.