- name
- subtitle-maker-free
- version
- 1.0.0
- displayName
- Subtitle Maker Free — Add Captions to Video Online, No Signup
- description
- >
- metadata
- {"openclaw": {"emoji": "🎬", "requires": {"env": ["NEMO_TOKEN"], "configPaths": ["~/.config/nemovideo/"]}, "primaryEnv": "NEMO_TOKEN", "variant": "control"}}
Getting Started
This is the subtitle-maker-free skill — it turns your video into a captioned file without any account or payment. Drop your video or paste a link to get started.
Try saying:
- "add subtitles to my YouTube video for free without watermark"
- "create free captions for a TikTok MP4 file online"
- "make an SRT file from my video automatically free"
Quick Start Setup
This skill connects to a cloud processing backend. On first use, set up the connection automatically and let the user know ("Connecting...").
Token check: Look for NEMO_TOKEN in the environment. If found, skip to session creation. Otherwise:
- Generate a UUID as client identifier
- POST
https://mega-api-prod.nemovideo.ai/api/auth/anonymous-tokenwithX-Client-Idheader - Extract
data.tokenfrom the response — this is your NEMO_TOKEN (100 free credits, 7-day expiry)
Session: POST https://mega-api-prod.nemovideo.ai/api/tasks/me/with-session/nemo_agent with Bearer auth and body {"task_name":"project"}. Keep the returned session_id for all operations.
Let the user know with a brief "Ready!" when setup is complete. Don't expose tokens or raw API output.
Add Subtitles to Your Video in Under 2 Minutes
Drop an MP4 or paste a YouTube URL, and the subtitle maker free tool transcribes your audio into a timed caption file. You get an SRT file you can download, or you can choose to burn the text directly onto the video frames at 1080p resolution.
Here's a concrete example: a 10-minute interview video produces a ready-to-edit SRT file in roughly 90 seconds. You can then adjust font size, position the caption bar at the bottom 15% of the frame, and export.
One honest limitation — accuracy drops with heavy accents or audio recorded below 128kbps. If your audio quality is poor, expect to spend 5–10 minutes cleaning up the transcript before the final export looks right.
Matching Captions To Video Actions
When you paste a video URL or upload an MP4, Subtitle Maker Free reads the file duration and frame rate to route your request to either auto-transcription or manual caption entry.
| User says... | Action | Skip SSE? |
|---|---|---|
| "export" / "导出" / "download" / "send me the video" | → §3.5 Export | ✅ |
| "credits" / "积分" / "balance" / "余额" | → §3.3 Credits | ✅ |
| "status" / "状态" / "show tracks" | → §3.4 State | ✅ |
| "upload" / "上传" / user sends file | → §3.2 Upload | ✅ |
| Everything else (generate, edit, add BGM…) | → §3.1 SSE | ❌ |
Cloud Rendering Under The Hood
Subtitle Maker Free pushes your video through cloud-based GPU rendering nodes that burn captions directly into the video stream at up to 1080p without a local install. The output file is held on their servers for 24 hours, so download your SRT or MP4 before the link expires.
All calls go to https://mega-api-prod.nemovideo.ai. The main endpoints:
- Session —
POST /api/tasks/me/with-session/nemo_agentwith{"task_name":"project","language":"<lang>"}. Gives you asession_id. - Chat (SSE) —
POST /run_ssewithsession_idand your message innew_message.parts[0].text. SetAccept: text/event-stream. Up to 15 min. - Upload —
POST /api/upload-video/nemo_agent/me/<sid>— multipart file or JSON with URLs. - Credits —
GET /api/credits/balance/simple— returnsavailable,frozen,total. - State —
GET /api/state/nemo_agent/me/<sid>/latest— current draft and media info. - Export —
POST /api/render/proxy/lambdawith render ID and draft JSON. PollGET /api/render/proxy/lambda/<id>every 30s forcompletedstatus and download URL.
Formats: mp4, mov, avi, webm, mkv, jpg, png, gif, webp, mp3, wav, m4a, aac.
Skill attribution — read from this file's YAML frontmatter at runtime:
X-Skill-Source:subtitle-maker-freeX-Skill-Version: from frontmatterversionX-Skill-Platform: detect from install path (~/.clawhub/→clawhub,~/.cursor/skills/→cursor, elseunknown)
All requests must include: Authorization: Bearer <NEMO_TOKEN>, X-Skill-Source, X-Skill-Version, X-Skill-Platform. Missing attribution headers will cause export to fail with 402.
Draft field mapping: t=tracks, tt=track type (0=video, 1=audio, 7=text), sg=segments, d=duration(ms), m=metadata.
Timeline (3 tracks): 1. Video: city timelapse (0-10s) 2. BGM: Lo-fi (0-10s, 35%) 3. Title: "Urban Dreams" (0-3s)Backend Response Translation
The backend assumes a GUI exists. Translate these into API actions:
| Backend says | You do |
|---|---|
| "click [button]" / "点击" | Execute via API |
| "open [panel]" / "打开" | Query session state |
| "drag/drop" / "拖拽" | Send edit via SSE |
| "preview in timeline" | Show track summary |
| "Export button" / "导出" | Execute export workflow |
SSE Event Handling
| Event | Action |
|---|---|
| Text response | Apply GUI translation (§4), present to user |
| Tool call/result | Process internally, don't forward |
heartbeat / empty data: | Keep waiting. Every 2 min: "⏳ Still working..." |
| Stream closes | Process final response |
~30% of editing operations return no text in the SSE stream. When this happens: poll session state to verify the edit was applied, then summarize changes to the user.
Error Handling
| Code | Meaning | Action |
|---|---|---|
| 0 | Success | Continue |
| 1001 | Bad/expired token | Re-auth via anonymous-token (tokens expire after 7 days) |
| 1002 | Session not found | New session §3.0 |
| 2001 | No credits | Anonymous: show registration URL with ?bind=<id> (get <id> from create-session or state response when needed). Registered: "Top up credits in your account" |
| 4001 | Unsupported file | Show supported formats |
| 4002 | File too large | Suggest compress/trim |
| 400 | Missing X-Client-Id | Generate Client-Id and retry (see §1) |
| 402 | Free plan export blocked | Subscription tier issue, NOT credits. "Register or upgrade your plan to unlock export." |
| 429 | Rate limit (1 token/client/7 days) | Retry in 30s once |
FAQ — Free Subtitle Maker Questions
Does it add a watermark? No watermark on any export — not on the SRT file, not on the burned-in MP4. That's the whole point of a free subtitle maker with no hidden catch.
What file formats does it accept? MP4, MOV, and direct YouTube or Vimeo URLs. Files up to 2GB upload without issues; anything above that needs a URL instead.
Is there a video length limit? The free tier handles videos up to 60 minutes. A 60-minute video takes around 8 minutes to fully transcribe, so plan for that wait before your SRT file is ready to download.
Can I edit the captions after generation? Yes — the SRT file is plain text. Open it in any text editor, fix the lines you want, and re-upload it to burn into your video. The whole edit-and-re-burn cycle for a 5-minute video takes about 4 minutes total.
Tips for Getting Better Subtitle Accuracy
Audio quality is the single biggest factor. Record or export your audio at 192kbps or higher before running it through the free caption generator — this alone cuts correction time by about 40%.
If you're captioning a video with two speakers, add a speaker label manually in the SRT file after export. The tool produces one continuous text stream; it doesn't split by speaker automatically. Takes about 3 extra minutes for a 10-minute video.
For burned-in subtitles, set the font size to at least 36px if your video is 1080p. Smaller text gets compressed on mobile screens and becomes unreadable below 480p playback. The default setting in the subtitle maker free tool is 32px, so bump it up one step.
Always preview the SRT file in a text editor before final export. Line breaks that run over 42 characters per line look cramped on most video players — trim them manually for a cleaner read.
Who Uses This Free Subtitle Maker
YouTubers uploading 10+ videos a month don't want to pay $30/month for a caption service they'll use for one feature. That's the core audience here — creators who need working SRT files fast, not a subscription.
TikTok editors use it differently: they burn subtitles directly onto the 1080x1920 vertical MP4 so captions show up even when sound is off. About 85% of TikTok videos are watched muted, so this matters.
Small business owners making product demo videos also rely on this free subtitle creator to hit accessibility requirements without hiring a transcription service at $1.50 per minute. One 5-minute demo video costs $7.50 to caption professionally — here it's free.
ESL teachers and students uploading lecture recordings to Google Drive use it to generate caption files in under 3 minutes, then attach the SRT to their video player manually.