explainroo is a free, open-source alternative to Synthesia for narrated explainers, lessons, and product demos. Tell a coding agent (software that writes and runs code from instructions) what video you need, and explainroo renders animated scenes on your computer.
Use explainroo to create animated scenes, diagrams, and product walkthroughs without a video-creation fee. Synthesia creates videos with AI avatars, which suit lessons built around a virtual presenter.
What the free explainroo kit includes
explainroo is an open-source kit under the MIT license. It creates an MP4 on your computer with narration and timed visuals. The video also includes background music and sound effects, and the kit checks for common layout and speech problems. It uses Kokoro, an open voice model, for narration. You do not need an account or API key. The narration is in English, with American and British English voices to choose from.
The core workflow has no video subscription or stated per-video fee; optional AI illustrations through OpenRouter cost per image, and the separate coding agent may have its own price. During setup, explainroo downloads the voice and timing models once. You do not need a graphics card.
The MIT license covers explainroo’s code. Product details do not say whether videos have a watermark or require attribution. They also do not explain whether rules differ for personal, educational, and business use. The license does not automatically grant rights to every voice, image, or other asset in a finished video. Check the relevant terms before publishing a video commercially.
Check what the free offer covers
The stated workflow lists no creation quota or export cap. The agent produces an MP4, and explainroo renders it on your computer. A coding agent or paid image provider may still have its own usage limits.
The kit requires a recent Node.js installation and FFmpeg. It also needs Chrome or Chromium. To avoid setting it up yourself, ask a coding agent that can run shell commands to install it. explainroo works with Claude Code, Codex, Pi, OpenCode, Gemini CLI, and other agents that can run commands. It works best with Claude Code.
Compare explainroo with Synthesia
The tools produce different kinds of videos. Synthesia turns scripts into videos with AI presenters. explainroo builds animated scenes around the narration, such as charts, code, icons, and screenshots. For training, choose based on whether learners need a presenter or visuals that follow the lesson.
Compare creation and editing
The coding agent writes script.md with the spoken words and scenes.js with instructions for drawing each scene. You can time a scene to a specific word, matching its visuals to the narration. Chrome draws the frames on an HTML canvas, and FFmpeg combines them into an MP4.
For a product demo, the agent can rebuild the product’s interface from its code or website, using the same colors, fonts, and button labels. A mouse pointer clicks through screens and types into fields as the narration explains each step. Tell the agent which product to demonstrate and where to find its code or website.
To revise a video, ask the agent to change the script or scenes. explainroo has no drag-and-drop editor. Choose one of five visual styles in video.json: paper, clean, chalk, blueprint, or midnight. The pace setting adjusts the narration, pauses, and animation speed. The available formats are wide, tall, portrait, and square. Tall, portrait, and square videos include word-by-word captions.
Use Synthesia when a virtual speaker should deliver the lesson. Use explainroo when diagrams or product screens need to appear at specific points in the narration. explainroo does not create talking avatars or AI-generated live-action footage, and it cannot edit existing camera footage.
Compare cost and access
The explainroo kit is free and open source, and its core video workflow has no per-video charge. You pay separately for an AI coding agent and for optional OpenRouter illustrations, which are charged per image. This article does not list Synthesia’s current prices or plan allowances, so check its terms before comparing costs. Compare export options, creation limits, and account requirements, not just the advertised price.
Choose explainroo or Synthesia by video style
Use explainroo for a short lesson when learners need to see a process, interface, or concept unfold alongside the narration. For example, a software trainer can ask an agent to demonstrate a product and explain each click. For a policy overview or general onboarding message centered on a presenter, Synthesia’s avatar format may suit the intended style better.
For explainers and lessons
Write a one-sentence learning goal, then ask the agent to make a short explainer about it. Focus each scene on one idea: use a diagram to show a relationship, a screenshot for a product step, or a few labels for a key term. Review the scene stills and contact sheet. Use the layout check to find overlapping or cut-off text. The speech check flags words the voice mispronounces.
To create a video with explainroo, give a command-capable coding agent this instruction, replacing the bracketed text:
Make me a short explainer video about [your topic]. Use explainroo: clone its GitHub repository, read AGENTS.md, and follow the steps.The agent sets up explainroo, creates and checks the video, then returns an MP4. If a scene is confusing, ask the agent to revise the script or visuals and check the new render. The agent cannot watch the finished video. Use the stills and checks to help with your review, then watch the MP4 yourself before publishing.
For regular video production
For occasional explainers and demos, explainroo’s core workflow avoids a per-video fee, but you need to set it up on your computer and use a coding agent. If you produce videos often, compare the time it takes to review and revise agent-generated scenes with the convenience and limits of a hosted plan. Before choosing a plan, check its current export rules, usage terms, and creation allowance.
When to use explainroo or Synthesia
- Use explainroo for visual explanations: It builds narrated scenes, diagrams, and product demos, then renders an MP4 on your computer.
- Account for separate costs: The core kit has no per-video fee, but a coding agent is separate and optional AI illustrations cost per image.
- Choose the presentation style deliberately: explainroo focuses on animated visuals; Synthesia is known for AI-presenter videos.
- Review rights and output: The MIT license covers explainroo’s code, while the product details do not specify all attribution, watermark, or asset-use terms.
Conclusion
explainroo’s core workflow is free for explainers, training lessons, and product demos with timed graphics or interface walkthroughs. You need to set it up on your computer and edit through an agent. It does not create avatars or live-action video.
Choose Synthesia when you need a virtual presenter, after checking its current plan and export terms. Choose explainroo when visuals matter more than an on-screen presenter. Review the finished MP4 before sharing it.
