Is my subtitle file uploaded anywhere?

No. Your subtitle file is read and converted directly in your browser. It is not uploaded to Stay Local Tools servers for processing.

How do I know the right Source and Target FPS?

The Source FPS is the frame rate the subtitle was originally timed for, and the Target FPS is the frame rate of the video you are watching. If you are not sure, common pairs to try are 25 and 23.976, or 30 and 29.97.

My subtitles are off by the same amount the whole way through. Is this the right tool?

No — if the gap stays the same size from start to finish, use the Subtitle Sync Adjuster instead. FPS Sync is for subtitles that start close but drift further out of sync as the video plays.

What if the drift is not a clean frame-rate ratio?

Try the Two-Point Sync tool instead. It lets you correct timing using two reference points anywhere in the file, which also fixes drift that does not match a standard frame-rate pair.

Subtitle FPS Converter

Fix subtitles that slowly drift out of sync because of a frame-rate mismatch.

Local Processing

Files stay on your device.

Choose File

or drag and drop files here

Supported: .srt, .smi, .sami, .vtt

Files stay on your device

Private by design

Your files are processed directly in your browser. They are not uploaded to Stay Local Tools servers for processing. Because the work happens on your device, your files stay with you unless you download or share them yourself.

Note: the website itself still loads normal web files, and may use analytics or ads later. The promise here is about the files and text you put into these tools.

How to Use

Choose your subtitle file (SRT, SMI or VTT).
Enter the Source FPS the subtitle was made for.
Enter the Target FPS you want to match.
Click Convert.
Download the converted file.

Why subtitles slowly drift

Video is often converted between frame rates — for example, a TV show made for 25 frames per second (common outside North America) played as a 23.976 fps file. Subtitles timed for one frame rate use slightly different second-lengths than the other, so they start out close but drift further apart the longer the video plays.

23.976 fps vs 25 fps

These are two of the most common frame rates for TV and film. Converting between them, or any other pair of frame rates, stretches or compresses every subtitle's timing by the same ratio, so subtitles that started in sync stay in sync all the way through.

Why this is different from a fixed delay

A fixed delay moves every subtitle by the same amount, which only helps when subtitles are off by a constant amount from the start. FPS drift gets worse over time, so it needs a stretch or compression instead — which is what this tool does.

Questions and Answers

: No. Your subtitle file is read and converted directly in your browser. It is not uploaded to Stay Local Tools servers for processing.
: The Source FPS is the frame rate the subtitle was originally timed for, and the Target FPS is the frame rate of the video you are watching. If you are not sure, common pairs to try are 25 and 23.976, or 30 and 29.97.
: No — if the gap stays the same size from start to finish, use the Subtitle Sync Adjuster instead. FPS Sync is for subtitles that start close but drift further out of sync as the video plays.
: Try the Two-Point Sync tool instead. It lets you correct timing using two reference points anywhere in the file, which also fixes drift that does not match a standard frame-rate pair.

Other Languages

Español

Ajustar FPS de subtítulos

Corrige subtítulos que se desincronizan poco a poco debido a un cambio de fotogramas por segundo. El archivo se procesa directamente en tu navegador y no se sube a los servidores de Stay Local Tools para el procesamiento.

Preguntas frecuentes

: No. Tu archivo de subtítulos se lee y se convierte directamente en tu navegador; no se sube a los servidores de Stay Local Tools.
: El FPS de origen es la velocidad para la que se hizo el subtítulo, y el de destino es la del video que ves. Si no lo sabes, prueba pares comunes como 25 y 23.976, o 30 y 29.97.
: No. Si el desfase se mantiene igual, usa Subtitle Sync. FPS Sync es para subtítulos que empiezan bien pero se desincronizan poco a poco.

Português (Brasil)

Ajustar FPS das legendas

Corrija legendas que vão saindo de sincronia aos poucos por causa de uma mudança de quadros por segundo. O arquivo é processado diretamente no navegador e não é enviado aos servidores do Stay Local Tools para processamento.

Perguntas frequentes

: Não. Seu arquivo de legenda é lido e convertido diretamente no navegador; ele não é enviado aos servidores do Stay Local Tools.
: O FPS de origem é a taxa para a qual a legenda foi feita, e o de destino é a do vídeo que você está assistindo. Pares comuns são 25 e 23.976, ou 30 e 29.97.
: Não. Se a diferença fica igual do início ao fim, use o Subtitle Sync. O FPS Sync é para legendas que começam certas mas vão saindo de sincronia aos poucos.

한국어

자막 FPS 변환

프레임레이트 차이로 인해 점점 어긋나는 자막의 타이밍을 보정할 수 있습니다. 파일은 브라우저에서 직접 처리되며 Stay Local Tools 서버에 업로드되지 않습니다.

자주 묻는 질문

: 아니요. 자막 파일은 브라우저에서 직접 읽고 변환되며 Stay Local Tools 서버에는 업로드되지 않습니다.
: Source FPS는 자막이 원래 맞춰진 프레임레이트이고, Target FPS는 지금 보는 영상의 프레임레이트입니다. 잘 모르면 25와 23.976, 또는 30과 29.97 조합을 시도해 보세요.
: 아니요. 어긋난 정도가 계속 같다면 Subtitle Sync를 사용하세요. FPS Sync는 처음엔 맞다가 점점 벌어지는 경우를 위한 도구입니다.