Subtitle workflow utility application

The challenge

As part of a large-scale subtitle translation workflow, I regularly worked with VTT subtitle files containing thousands of timestamped entries.

Several recurring challenges slowed down the translation process:

• large VTT files often exceeded the practical limits of AI translation tools
• translated subtitle segments had to be manually merged back together
• timestamp validation was difficult and time-consuming
• existing tools either lacked the required functionality or required complex installation and setup

The workflow needed a simple, reliable solution that could support subtitle translation projects at scale.

The solution

To optimise the workflow, I designed and built a browser-based utility application specifically for subtitle management.

The application was developed through AI-assisted development workflows using Claude and focused on three core functions:

• splitting large subtitle files into manageable sections
• merging translated subtitle files automatically
• validating timestamp integrity between source and translated files

The result was a lightweight tool that could be used directly in the browser without installation, allowing subtitle workflows to be completed faster and with fewer errors.

Workflow overview

Original VTT file
        ↓
Split into sections
        ↓
AI translation
        ↓
Merge translated files
        ↓
Timestamp validation
        ↓
Final VTT output

The workflow reduced manual handling throughout the subtitle translation process while introducing a reliable quality-control step for timestamp verification.

Results & impact

Workflow improvements

• reduced subtitle file preparation time significantly
• eliminated manual merging of translated files
• introduced automated timestamp validation
• reduced translation failures caused by oversized subtitle files
• standardised file naming and workflow consistency

Quality improvements

• improved timestamp accuracy
• reduced risk of synchronization errors
• simplified quality assurance processes
• created repeatable translation workflows

Accessibility

The application runs entirely in the browser with no installation requirements, making it easy to share and use across teams.

Before vs after

	Previous workflow	Utility application
Large VTT files	Manual handling	Automated splitting
File merging	Manual copy/paste	One-click merge
Timestamp validation	Manual review	Automated comparison
Translation readiness	Variable	Standardised
Error detection	Manual	Instant
Scalability	Moderate	High