Question 1

How do I sync subtitles to a video?

Accepted Answer

Upload your video and subtitle file to SyncFlow, then use the global offset slider to shift subtitle timing. For instant syncing, pause the video at a spoken word and click the SYNC TO THIS MOMENT button. The tool auto-calculates the correct offset. Fine-tune with ±100ms or ±1s nudge buttons for precision.

Question 2

What is subtitle drift?

Accepted Answer

Subtitle drift is when subtitles start in sync with the video but gradually become misaligned as the video progresses. This is usually caused by a framerate mismatch between the video and the subtitle file — for example, subtitles created for 23.976 fps video being used on a 25 fps version. SyncFlow's linear drift calibration fixes this using two anchor points.

Question 3

How do I fix out-of-sync subtitles?

Accepted Answer

Use SyncFlow's global offset slider to shift all subtitles forward or backward. If subtitles appear too early, use a positive offset. If too late, use a negative offset. For drift issues where sync worsens over time, use the Linear Drift Calibration panel with two anchor points.

Question 4

What is an SRT file?

Accepted Answer

SRT (SubRip Text) is the most common subtitle format. It contains sequential subtitle entries with index numbers, timestamps in HH:MM:SS,MMM format, and the subtitle text. SRT files are plain text and can be opened in any text editor. SyncFlow fully supports importing and exporting SRT files.

Question 5

What is a VTT file?

Accepted Answer

VTT (WebVTT) is a modern subtitle format developed by the W3C for web video. It uses timestamps in HH:MM:SS.MMM format (dot instead of comma) and supports styling cues. VTT is the standard format for HTML5 video players. SyncFlow supports both importing and exporting VTT files.

Question 6

What is the difference between SRT and VTT?

Accepted Answer

The main differences are: SRT uses a comma (,) as the millisecond separator while VTT uses a dot (.). SRT has index numbers for each cue while VTT optionally uses them. VTT supports CSS styling, cue settings (vertical position, alignment), and metadata headers. SRT is more universally supported across media players. SyncFlow can convert between both formats.

Question 7

How do I open an SRT file?

Accepted Answer

SRT files are plain text and can be opened with any text editor like Notepad, Notepad++, VS Code, or Sublime Text. To use an SRT file with a video, place both files in the same folder with the same name (e.g., video.mp4 and video.srt). Most media players like VLC, MPC-HC, and Plex will auto-load the subtitle file.

Question 8

How do I edit an SRT file?

Accepted Answer

You can edit SRT files in any text editor by modifying the timestamps or text directly. For bulk editing and syncing, use SyncFlow — it provides a visual interface with inline text editing, global offset adjustment, and drift calibration. You can click on any cue in the registry list and edit its text directly in the textarea.

Question 9

How do I create subtitles for a video?

Accepted Answer

Use an online subtitle editor like SyncFlow to create subtitles. Upload your video, then use the inline cue editor to type subtitle text with precise timestamps. You can click on any cue row to jump the video to that timestamp, making it easy to match text to audio. Once done, export as SRT or VTT.

Question 10

What is the best free subtitle sync tool?

Accepted Answer

SyncFlow is the best free subtitle sync tool because it runs mostly in your browser with no account and no limits. It includes tap-to-sync, linear drift calibration, inline text editing, SRT/VTT conversion, and real-time visual feedback. Video processing stays local while AI transcription uses a secure Cloudflare proxy.

Question 11

How do I fix subtitle timing?

Accepted Answer

Use SyncFlow's global offset slider to shift all subtitle timestamps forward or backward. The slider provides real-time visual feedback — subtitles update instantly on the video overlay as you drag. For microsecond precision, use the millisecond input or ±100ms nudge buttons.

Question 12

What causes subtitles to go out of sync?

Accepted Answer

Common causes include: framerate mismatch (23.976 vs 25 fps), different video cuts or edits, different starting points (some releases include studio logos), incorrect manual timing by the subtitle creator, and video encoding errors. SyncFlow's global offset handles fixed misalignment while linear drift calibration handles progressive desync.

Question 13

How do I fix subtitle drift in VLC?

Accepted Answer

In VLC, you can use the G and H keys to temporarily adjust subtitle timing while watching, but this resets when you close the file. For a permanent fix, use SyncFlow to export a corrected SRT file with proper drift correction applied, then load the fixed file in VLC.

Question 14

How do I sync subtitles in VLC?

Accepted Answer

In VLC, press G to delay subtitles (make them appear later) and H to advance subtitles (make them appear earlier). Each press adjusts by 50ms. This adjustment is temporary and resets when you close the file. For permanent sync, use SyncFlow to export a properly timed SRT file.

Question 15

Subtitle offset vs drift — what's the difference?

Accepted Answer

Offset is a fixed time shift applied equally to all subtitles (e.g., all subtitles are +3 seconds late). Drift is progressive misalignment that gets worse over time (e.g., subtitles at the start are correct but by the end they're 10 seconds off). SyncFlow handles both: offset via the global slider, drift via the two-point linear calibration system.

Question 16

How do I delay subtitles?

Accepted Answer

In SyncFlow, drag the offset slider to the right (positive values) to delay all subtitles. Each +1 second means subtitles appear 1 second later. You can also use the +100ms and +1s nudge buttons for precise adjustments. The subtitle overlay updates instantly so you can see the effect in real-time.

Question 17

How do I make subtitles appear earlier?

Accepted Answer

In SyncFlow, drag the offset slider to the left (negative values) to make subtitles appear earlier. For example, −2 seconds shifts all subtitles to appear 2 seconds sooner. Use the −100ms and −1s nudge buttons for fine-grained control.

Question 18

How do I fix subtitles that appear too early?

Accepted Answer

If subtitles appear before the person speaks, use a positive offset in SyncFlow to delay them. For example, if subtitles are 3 seconds early, set the offset to +3 seconds. The subtitles will shift forward by 3 seconds, matching the audio.

Question 19

How do I fix subtitles that appear too late?

Accepted Answer

If subtitles appear after the person speaks, use a negative offset in SyncFlow to advance them. For example, if subtitles are 4 seconds late, set the offset to −4 seconds. The subtitles will shift backward by 4 seconds to match the spoken audio.

Question 20

What is frame rate mismatch in subtitles?

Accepted Answer

Frame rate mismatch occurs when subtitles created for a video at one frame rate (e.g., 23.976 fps) are used with a video at a different frame rate (e.g., 25 fps). This causes the subtitles to progressively drift out of sync because each frame has a slightly different duration. SyncFlow's linear drift calibration corrects this mathematically.

Question 21

How do I fix 23.976 vs 25 fps subtitle drift?

Accepted Answer

SyncFlow's linear drift calibration can fix this. Set Anchor Point A at an early cue with its correct time. Set Anchor Point B at a late cue with its correct time. The tool calculates a scaling factor that proportionally corrects all intermediate timestamps, accounting for the framerate ratio (25/23.976 ≈ 1.0427).

Question 22

Can I edit subtitle text in SyncFlow?

Accepted Answer

Yes. After loading subtitles, scroll through the Cues Registry panel on the right side. Each cue has an editable textarea where you can modify the subtitle text directly. Changes are applied immediately and will be included when you export the corrected subtitle file.

Question 23

How do I download subtitles for movies?

Accepted Answer

Popular websites for downloading subtitles include OpenSubtitles, Subscene, Podnapisi, and YIFY Subtitles. Download the SRT or VTT file that matches your video release. If the downloaded subtitles are out of sync, use SyncFlow to adjust them using the offset slider or drift calibration.

Question 24

How do I convert SRT to VTT?

Accepted Answer

In SyncFlow, load your SRT file, then in the Export section change the format dropdown from SRT to VTT. Click Save Corrected Subtitles to download the file in VTT format. SyncFlow automatically handles the timestamp format conversion (comma to dot separator) and adds the WEBVTT header.

Question 25

How do I convert VTT to SRT?

Accepted Answer

In SyncFlow, load your VTT file, then in the Export section select SRT format. Click Save Corrected Subtitles to download. SyncFlow handles all format differences including the WEBVTT header removal, timestamp separator conversion, and cue numbering.

Question 26

How do I add subtitles to a video permanently?

Accepted Answer

To permanently embed subtitles into a video (hardcoding), you need video editing software like HandBrake, FFmpeg, or DaVinci Resolve. First, sync your subtitles using SyncFlow and export a corrected SRT file. Then use FFmpeg or your editor of choice to burn the subtitles into the video stream.

Question 27

How do I sync subtitles online for free?

Accepted Answer

SyncFlow is a completely free online subtitle sync tool. Upload your video and subtitle file to your browser (nothing is uploaded to servers), use the visual sync controls, and download the corrected file. No registration, no limits, no watermarks.

Question 28

Is there a free subtitle synchronizer?

Accepted Answer

Yes, SyncFlow is a completely free subtitle synchronizer. It runs entirely in your browser with no server-side processing. Features include global offset adjustment, tap-to-sync, linear drift calibration, inline text editing, and SRT/VTT conversion — all at no cost.

Question 29

How do I fix subtitles without re-downloading?

Accepted Answer

Use SyncFlow to adjust your existing subtitle file. Upload it alongside your video, use the offset slider or drift calibration to fix the timing, then export the corrected version. No need to search for a new subtitle file online.

Question 30

What encoding do SRT files use?

Accepted Answer

SRT files commonly use UTF-8, UTF-16 (with BOM), or Windows-1252 (Latin-1) encoding. SyncFlow auto-detects the encoding of your subtitle file, so accented characters in languages like French, Spanish, German, or Turkish display correctly without garbled text.

Question 31

Why are special characters broken in my subtitles?

Accepted Answer

Special characters (é, ü, ñ, ç) appear broken when the subtitle file's encoding doesn't match what the player expects. SyncFlow auto-detects the encoding of your file — whether UTF-8, UTF-16, or Windows-1252 — and displays the text correctly. Always export in UTF-8 for maximum compatibility.

Question 32

How do I fix encoding issues in subtitles?

Accepted Answer

SyncFlow automatically detects and handles different subtitle encodings. If you're viewing a file with garbled characters, load it into SyncFlow — the encoding detection will decode it correctly. Then export in UTF-8 format, which is universally compatible with all media players.

Question 33

How do I align subtitles with audio?

Accepted Answer

SyncFlow's tap-to-sync feature makes this easy: pause the video at a clearly spoken word, then click the SYNC TO THIS MOMENT button. The tool automatically calculates the offset needed to align all subtitles with the audio. For drift issues, use the linear calibration panel with two anchor points.

Question 34

How does SyncFlow's tap-to-sync work?

Accepted Answer

Tap-to-sync works by reading the current video playhead position and finding the nearest subtitle cue. It then calculates the exact offset needed to make that subtitle's start time match the playhead position. This offset is applied globally to all subtitles, instantly aligning the entire file.

Question 35

What is linear calibration for subtitles?

Accepted Answer

Linear calibration (also called drift correction) uses two anchor points to fix subtitles that progressively drift out of sync. You mark the correct time for an early subtitle (Anchor A) and a late subtitle (Anchor B). SyncFlow then calculates a scaling factor and linear offset that corrects all subtitles proportionally.

Question 36

How do I fix progressive subtitle drift?

Accepted Answer

Open the Fix Progressive Drift panel in SyncFlow. Set Anchor Point A at an early cue (e.g., cue #5) and enter the correct time it should appear. Set Anchor Point B at a late cue (e.g., cue #800) with its correct time. Click Apply Linear Calibration — the tool will mathematically correct all timestamps.

Question 37

How do I sync subtitles for a 2-hour movie?

Accepted Answer

Load your video and SRT file into SyncFlow. Start by checking subtitle timing at the beginning: pause at a spoken line and use tap-to-sync or the slider. Then check the middle and end of the movie. If timing worsens progressively, use the linear drift calibration panel to fix framerate mismatches. Export the corrected SRT when done.

Question 38

Can I sync subtitles without uploading files?

Accepted Answer

Yes. SyncFlow processes video and subtitles entirely client-side. Offset adjustment, drift calibration, inline editing, and export all work locally in your browser. AI transcription separately sends audio through a secure Cloudflare proxy to Groq's Whisper-large-v3-turbo API. Audio is processed in memory and never stored on any server. Your original video file never leaves your computer.

Question 39

Is SyncFlow free to use?

Accepted Answer

Yes, SyncFlow is completely free with no hidden costs. There are no usage limits, no watermarks, no account required, and no subscription. You can sync as many subtitle files as you want, for videos of any length, without paying anything.

Question 40

Does SyncFlow store my video or subtitle files?

Accepted Answer

No. Offset adjustment, drift calibration, inline editing, and export all work locally in your browser. AI transcription separately sends audio through a secure Cloudflare proxy to Groq's Whisper-large-v3-turbo API. Audio is processed in memory and never stored on any server. Once you close the browser tab, all data is cleared. The only data stored is your offset and font size preferences in your own browser's localStorage.

Question 41

What browsers does SyncFlow support?

Accepted Answer

SyncFlow works on any modern browser: Chrome, Firefox, Edge, Safari, and Opera. It requires JavaScript and the FileReader API, which all modern browsers support. For the best experience, use the latest version of Chrome or Edge.

Question 42

How do I export synced subtitles?

Accepted Answer

After syncing your subtitles, click the Save Corrected Subtitles button in the Export section. Choose between SRT or VTT format. The file will download automatically with a name like 'videoname_synced.srt'. The exported file includes all your offset and drift adjustments.

Question 43

What is the best subtitle format for YouTube?

Accepted Answer

YouTube supports both SRT and VTT formats. VTT (WebVTT) is recommended because it natively supports the WebVTT format that YouTube's player uses internally. You can convert any SRT file to VTT using SyncFlow's export feature.

Question 44

How do I fix subtitle timestamps manually?

Accepted Answer

In SyncFlow, you can edit individual cue timestamps by using the offset slider (shifts all cues) or by adjusting specific cues in the Cues Registry. For single-cue fixes, click on a cue row to jump the video to that timestamp, then use the millisecond offset input for precise adjustments.

Question 45

How do I check if subtitles are synced correctly?

Accepted Answer

Play the video in SyncFlow and watch the Live Status bar. It shows the current playhead time and the active subtitle cue. The Current Cue Panel displays the exact subtitle text and its start/end times. If the green active dot appears when dialogue is spoken, your subtitles are synced.

Question 46

What does global offset mean for subtitles?

Accepted Answer

Global offset is a single time value (in milliseconds) that is added to every subtitle's start and end time. A positive offset delays all subtitles, a negative offset advances them. This is the simplest way to fix subtitles that are consistently early or late. SyncFlow provides a slider, number input, and nudge buttons for setting the offset.

Question 47

How do I use anchor points for subtitle calibration?

Accepted Answer

In SyncFlow's drift calibration panel, identify two well-known spoken lines — one near the start of the video and one near the end. For each anchor point, enter the cue index and the correct time (in seconds) when the line should appear. Click Apply Linear Calibration to correct all subtitles proportionally.

Question 48

Can I sync multiple subtitle files at once?

Accepted Answer

SyncFlow processes one subtitle file at a time. If you need to sync multiple files with the same offset (e.g., an entire TV series), note the offset value from the first file and apply the same value to subsequent files. The offset is displayed clearly in the controls panel.

Question 49

How do I reset subtitles to original timing?

Accepted Answer

Click the Reset button next to the offset controls to set the global offset back to 0 (original timing). If you've applied drift calibration, click Clear Calibration in the drift panel to reset the scale factor and linear offset. To start completely fresh, click the New Project button in the header.

Question 50

What subtitle formats does SyncFlow support?

Accepted Answer

SyncFlow supports SRT (SubRip) and VTT (WebVTT) formats for both import and export. It automatically detects the format of your uploaded file and sets the export format accordingly. You can change the export format before downloading to convert between SRT and VTT.

Question 51

How does Auto-Save work in SyncFlow?

Accepted Answer

SyncFlow automatically saves your progress to your browser's LocalStorage every 30 seconds. This means if you refresh the page, close your browser, or your computer crashes, your work will be automatically restored the next time you open the site. You can manually clear this data using the 'Clear All Saved Data' button in the Project Data & Persistence card.

Question 52

How do I translate my subtitles using AI?

Accepted Answer

SyncFlow uses Groq's Llama-3.3-70B AI to translate subtitles. Select your target language in the AI Translation card and click 'Translate All Cues'. The tool processes your subtitles in chunks to ensure high-quality translation while preserving your original timing. You can undo the translation using Ctrl+Z if needed.

Question 53

How does the Auto-Transcribe feature work?

Accepted Answer

SyncFlow's Auto-Transcribe uses Whisper-large-v3-turbo through a secure Cloudflare proxy to Groq's API to generate subtitles. Your audio is processed in memory and never stored on any server. Once transcription is complete, every recognized phrase becomes an editable cue in the Cues Registry, ready for fine-tuning.

Question 54

Does Auto-Transcribe need an internet connection?

Accepted Answer

Yes. AI transcription requires an internet connection to send audio through a secure Cloudflare proxy to Groq's Whisper-large-v3-turbo API. All other syncing features (offset, drift calibration, manual editing) work completely offline.

Question 55

Is my audio data private?

Accepted Answer

Absolutely. Audio is sent through a secure Cloudflare proxy to Groq's API and processed in memory. No audio data, file fragments, or transcriptions are ever stored on any server. Your original video file never leaves your computer.

Question 56

How do I use the waveform preview?

Accepted Answer

The waveform preview visualizes your video's audio as a colorful bar graph that builds in real time during playback. Audio peaks are accumulated progressively, so you can see the sonic landscape of your entire video as it plays. Click anywhere on the waveform to seek instantly to that point in the video. Subtitle cue boundaries are overlaid as colored markers directly on the waveform, giving you a visual map of where each subtitle starts and ends. This makes it easy to spot gaps, overlaps, or misaligned cues at a glance.

Question 57

What keyboard shortcuts does SyncFlow support?

Accepted Answer

SyncFlow offers a full set of keyboard shortcuts for efficient subtitle editing: Space — Play/Pause. Left/Right Arrow — Seek ±5 seconds. Tab — Jump to next cue. Shift+Tab — Jump to previous cue. [ and ] — Global offset ±100ms. Shift+Up Arrow — Nudge selected cue 100ms earlier. Shift+Down Arrow — Nudge selected cue 100ms later. I — Set Loop Marker A. O — Set Loop Marker B. L — Toggle A-B Loop. Ctrl+Z — Undo last action (offset, text edit, or calibration). ? — Toggle the help overlay.

Question 58

How do I save and load projects?

Accepted Answer

SyncFlow lets you save your entire workspace as a .syncflow project file. This JSON-based file captures everything: all subtitle cues with their original timestamps, the current global offset value, any drift calibration settings, and the video filename reference. To save, click Save Project (.syncflow) in the Export card — the file downloads instantly. To restore your work later, simply drag the .syncflow file onto the SyncFlow interface or use the Load Project button. Your subtitles and all adjustments come back exactly as you left them.

Question 59

What is the linear drift calibration?

Accepted Answer

Linear drift calibration is SyncFlow's advanced solution for progressive subtitle misalignment caused by framerate mismatches. When subtitles created for a 23.976 fps video are used on a 25 fps version, each frame is slightly shorter, causing subtitles to drift slowly out of sync. The drift accumulates linearly — a few seconds off by the end of a 2-hour movie. Linear drift calibration fixes this by applying a mathematical scale factor to all timestamps, calculated from two anchor points. It works like a rubber band: you pin down the correct time at the start and end, and all intermediate cues stretch proportionally into place.

Question 60

How do I use the anchor points for drift calibration?

Accepted Answer

Using anchor points is straightforward: 1) Find a subtitle cue near the beginning of the video. Enter its cue index number in Anchor A's 'Cue Index' field, then press the 'Current' button to capture the correct playhead time into the time field. 2) Find another subtitle cue near the end of the video. Enter its cue index in Anchor B's 'Cue Index' field and press 'Current' to capture its correct time. 3) Click 'Apply Linear Calibration' — SyncFlow computes the scaling factor and corrects every cue proportionally.

Question 61

Can I edit individual subtitle lines?

Accepted Answer

Absolutely. Scroll through the Cues Registry panel on the right side of the SyncFlow interface. Each subtitle entry is displayed with its index number, timestamps, and a textarea containing the subtitle text. Simply click inside any textarea and edit the text directly — changes apply immediately and are reflected in the video overlay. This is perfect for fixing typos, adjusting line breaks, correcting transcription errors, or rewriting dialogue for clarity. All edits are preserved when you export the corrected SRT or VTT file.

Question 62

What happens if my video has no audio track?

Accepted Answer

If your video file lacks an audio track (or has an unsupported audio codec), the waveform preview will remain empty and the Auto-Transcribe button will be disabled. Don't worry — all other SyncFlow features work perfectly fine! You can still load subtitle files, adjust the global offset, apply drift calibration using the standard visual playback cues, and export corrected subtitles. The waveform and transcription features are enhancements, not requirements. For offset and drift syncing, you only need the video's playback timeline.

Question 63

How does SyncFlow handle different file encodings?

Accepted Answer

SyncFlow automatically detects the character encoding of subtitle files you load. It supports UTF-8 (with or without BOM), UTF-16 (both little-endian and big-endian with BOM markers), and Windows-1252 (Latin-1) encoding. Accented characters, special symbols, and non-Latin scripts are decoded correctly without garbled text. When you export your corrected subtitles, SyncFlow always saves in clean UTF-8 format — the universal standard that provides maximum compatibility across all media players, operating systems, and web platforms.

Question 64

What is the A-B Loop feature?

Accepted Answer

The A-B Loop lets you repeatedly play a specific section of the video. Press I to set the loop start point (Marker A) and O to set the loop end point (Marker B). Press L to toggle loop mode on and off. This is useful for fine-tuning subtitle timing for a difficult section — the video will automatically seek back to Marker A each time it reaches Marker B, letting you focus on getting those few cues exactly right.

Subtitle Syncing FAQ