Table of Contents
1. What is SRT Format?
SRT (SubRip Subtitle) is the most widely supported subtitle format in the world. Originally created by the SubRip software, it has become the de facto standard for subtitle files due to its simplicity, universal compatibility, and plain text structure.
Key Advantages of SRT Format
- • Universal Compatibility: Supported by virtually all video players and platforms
- • Simple Structure: Plain text format that's easy to create and edit
- • Small File Size: Minimal overhead compared to other subtitle formats
- • Human Readable: Can be opened and edited in any text editor
- • Platform Independent: Works across all operating systems and devices
Technical Specifications
- File Extension: .srt
- Encoding: UTF-8 (recommended), UTF-16, or ANSI
- Line Endings: Windows (CRLF), Unix (LF), or Mac (CR)
- Maximum File Size: No technical limit (practical limit ~10MB for most players)
- Character Limit: Typically 32-42 characters per line for optimal readability
2. SRT File Structure
Every SRT file consists of subtitle blocks, each containing four essential elements in a specific order:
Basic SRT Structure
1 00:00:01,000 --> 00:00:05,500 This is the first subtitle line. This is the second line of the same subtitle. 2 00:00:05,500 --> 00:00:09,000 This is the second subtitle. 3 00:00:09,000 --> 00:00:12,750 And this is the third subtitle with multiple lines of text.
Element Breakdown
1. Sequence Number
Sequential number starting from 1, incrementing for each subtitle block.
2. Timing Information
Start time --> End time in HH:MM:SS,mmm format.
3. Subtitle Text
One or more lines of subtitle text (maximum 2 lines recommended).
4. Blank Line
Empty line separating each subtitle block.
3. Timing Format Specification
SRT timing uses a precise format that ensures accurate synchronization with video content.
Timing Format: HH:MM:SS,mmm
- • HH: Hours (00-99, zero-padded)
- • MM: Minutes (00-59, zero-padded)
- • SS: Seconds (00-59, zero-padded)
- • mmm: Milliseconds (000-999, zero-padded)
- • Separator: Comma (,) for milliseconds, colon (:) for other units
- • Arrow: Space-arrow-space ( --> ) between start and end times
Timing Examples
Valid timing formats: 00:00:01,000 --> 00:00:05,500 00:01:30,250 --> 00:01:35,750 01:23:45,123 --> 01:23:50,456 Invalid timing formats: 0:0:1,0 --> 0:0:5,5 (not zero-padded) 00:00:01.000 --> 00:00:05.500 (period instead of comma) 00:00:01,000->00:00:05,500 (missing spaces around arrow)
Timing Best Practices
- Minimum Duration: 1.5 seconds for readability
- Maximum Duration: 6 seconds to maintain engagement
- Gap Between Subtitles: 250ms minimum for processing
- Reading Speed: 200-250 words per minute for average viewers
- Overlap Prevention: Ensure end time of one subtitle doesn't exceed start time of the next
4. Text Formatting Rules
While SRT is primarily a plain text format, it supports basic formatting tags for enhanced presentation.
Supported Formatting Tags
<b>Bold text</b> <i>Italic text</i> <u>Underlined text</u> <font color="#FF0000">Colored text</font> <font size="18">Sized text</font>
Formatting Compatibility Warning
Not all video players support SRT formatting tags. For maximum compatibility, use plain text only. Test your formatted subtitles across different players before distribution.
Character Guidelines
- Line Length: 32-42 characters per line for optimal readability
- Line Count: Maximum 2 lines per subtitle block
- Special Characters: Use Unicode for accented characters and symbols
- Speaker Identification: Use dashes (-) or speaker names in brackets [SPEAKER]
- Sound Effects: Use brackets or parentheses: [MUSIC] or (door slams)
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