KiraNeiro
KiraNeiro is a free web app that lets you create lightweight, animated content from music, illustrations, text, and voice — without video editing software. Just use your browser. This page covers what you can make, how to use it, how it works, and common pitfalls.
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A tool for creators to turn music, art, text, and voice into animated content without learning video editing software.
The Problem It Solves
Creators who have music, illustrations, text, or narration they want to share often can't afford the time, cost, or learning curve of mastering full-featured video editing software just to animate them. Existing video tools are built around video files and are too cumbersome for everyday creative work. KiraNeiro removes that barrier — you can start creating with nothing but a browser.
Types of Content You Can Make
| Type | Description | Main Users |
|---|---|---|
| Music Video (MV) | Animate illustrations and lyrics to music | Singer-songwriters, vocaloid producers, illustrators |
| Explainer Video | Sync narration with diagrams and text | Educators, explainer creators |
| Short Story | Combine text, narration, and illustrations into a short narrative | Writers, narration creators |
| Reading Video | Sync read-aloud audio with on-screen text | Authors, audiobook creators |
| Picture Book | Combine multiple pages of art, text, and optional narration into one piece | Picture book authors, comic creators |
| Voice + Photo | Minimal format: one photo plus one audio track | Memory sharing, casual creators |
Design Philosophy (How It Differs from Other Video Editors)
Server-Free Design (Respecting Copyright & Privacy)
KiraNeiro only provides the playback engine. The app never sends or stores media files you load into your browser on our servers — everything happens client-side in your browser. Your projects live in your own local storage or on cloud storage you control (like GitHub). That means you own and manage your content's copyright and sharing rights.
Price
Completely free with no feature limits (donation-based). When export finishes, you can optionally donate or share on social media — but none of that is mandatory, and there are no interruptions during creation.
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Editor (creation interface)
We verify the editor's functionality on three primary target environments: Windows + Edge, Android + Chrome, and iPad + Safari. For other browser and OS combinations, the code isn't designed to block them (there are no explicit restrictions), but we haven't performed formal verification testing. This means they work, but we haven't done comprehensive testing to confirm all features function correctly. It's "not formally verified" rather than "confirmed not supported."
Viewer (playback only)
The viewer page for playing published content works on all major browsers (Chrome, Edge, Firefox, Safari) on desktop and mobile. Playback doesn't require the special APIs that creation does, so viewers can use any modern browser.
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Start from the homepage by clicking "Open Editor," which takes you to the project creation screen. Choose the type of content you want to make.
Project Types You Can Create
| Type | Wizard Flow |
|---|---|
| Lyrics MV | Add audio (music) → add character/background art → enter lyrics and set timing per line |
| Picture Book | Set page count → add narration audio (optional), which auto-distributes page display times based on audio length → add background art and text to each page |
| Voice + Photo | Add one photo (as full-canvas background) → add one audio track (upload or record) → audio length becomes your total playback time — simplest workflow |
Each wizard shows step-by-step guidance so you can reach a complete project without video editing knowledge. After finishing the wizard, you move to the full timeline editor and can keep editing freely. You can also skip the wizard and start from a blank project if you prefer.
Canvas Size for Your Platform
When creating a project (or anytime after), just pick your target platform and the canvas aspect ratio is set automatically.
| Platform | Size | Aspect Ratio |
|---|---|---|
| YouTube / Niconico / Bilibili | 1920×1080 | 16:9 (landscape) |
| TikTok | 1080×1920 | 9:16 (portrait) |
| YouTube Shorts | 1080×1920 | 9:16 (portrait) |
| Instagram Reels / Stories | 1080×1920 | 9:16 (portrait) |
| Spotify Canvas | 1080×1920 | 9:16 (portrait) |
| X | 1080×1080 | 1:1 (square) |
| Instagram Feed (1:1) | 1080×1080 | 1:1 (square) |
| Instagram Feed (4:5) | 1080×1350 | 4:5 (portrait) |
| Custom | Any size | Any size you specify |
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You combine three types of assets on the timeline: images, audio, and text.
Supported Formats
Extracting Audio from Video Files
Drag an MP4 (like an Android screen recording) or MOV (like an iOS screen recording) file directly into the app on your PC. The video part is discarded and only the audio track is extracted and imported as a normal audio asset. You don't need to split it out in a video editor first. On smartphones, drag-and-drop doesn't work well, so use the file picker (file selection dialog) instead to add video files.
Recording Audio with Your Microphone
While your background audio is playing, you can record vocals or narration directly in your browser using your microphone. The browser automatically checks whether recording is supported, and if not, the recording button won't appear at all. Chrome, Edge, and Firefox all support this, as do Safari on iOS and macOS in MP4 format. Recorded audio is treated the same as other added audio assets for timing and layering. Like all assets in KiraNeiro, your recorded audio never touches our servers — it stays in your project.
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The timeline at the bottom of the screen is where you arrange multiple tracks (images, text, audio) along a time axis.
Basic Operations
Automatic Keyframe Recording
You don't need to click an "Add Keyframe" button. Just drag an object on the canvas to move, scale, or rotate it, and a keyframe is automatically recorded at that timeline position. Motion between keyframes is interpolated with Bezier curves, and you can choose ease-in and ease-out. Each object can also loop (repeat a section) if you enable it.
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Change how objects look and move over time — manipulate them directly on the canvas in the center of the screen. Adjust opacity, scale, images, animations, and effects.
Selecting and Manipulating Objects
Click on an object in the canvas to select it. Drag it to move it, or use the handles around the selected object to resize or rotate. To select multiple objects simultaneously, hold Shift and click each object you want to select, then drag them together to move as a group or use the handles to scale them together.
Preset Animations
Objects have one-click entrance and exit animations (bounce in, rotate in, slide in, etc.). Applying one auto-generates multiple keyframes for position, scale, rotation, and opacity, which you can then tweak individually.
Swapping Images (Drawing Substitution)
Switch which image a character object displays at different times. This lets you do facial expressions, mouth movement, or costume changes using multiple image files within a single object.
Opacity & Scale Animation
Fade objects in and out, or scale them up and down over time. You can also set custom background colors and images for the canvas itself.
Image Effects
Apply visual effects to images — blur, sepia, black & white, color grading, etc. Pick a preset and parameters auto-populate; you can tweak them after. Heavy effects can be toggled on/off so they work smoothly even on low-end PCs like Chromebooks.
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Lyrics, subtitles, and narration are organized as blocks (lines or paragraphs), and timing is adjusted per block.
Block-Level Timing
Each line of lyrics or paragraph of text gets its own timing slot. You adjust start and end times for each block individually. Use the preview to see how it syncs with the audio while you fine-tune. On the timeline, you can drag a text block to move it in time, but you can't resize it by dragging the edges — block width is determined by content and timing. If you add or remove lines, the timing slots change, so review the timing panel after editing.
Fonts & Styling
Customize font, text color, and size. Add fade-in/fade-out animation. Create decorative text styles with gradient fills, shadows, and outlines. There's also a "Random" button in the font dialog that suggests random styling combinations.
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Noise Reduction
Apply a filter to your main audio track to reduce environmental noise picked up during recording.
Sound Effects
Add reverb and other sound effects to your main audio track. The effect is consistent across preview, export, and live playback. Heavy processing can be toggled to ensure smooth playback on budget PCs.
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Auto-save → Work Folder (Internal)
KiraNeiro continuously auto-saves your project to an internal work folder (Origin Private File System). You won't see it in Explorer or Finder — it's hidden.
Ctrl+S → .kneiro File
Press Ctrl+S (or go to File → Save As) to save your project as a .kneiro file to a location you choose. This is the portable, shareable project file. Auto-save does not update this file. If you want to keep a backup or continue on another device, save it this way.
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Save As (.kneiro) — Project File
Saves the full project so you can re-edit it later in KiraNeiro.
Export Video (MP4)
Renders to MP4 using WebCodecs where available (up to 1920×1080, no export limits). Environments without WebCodecs support — including Firefox, some Safari versions, and iOS Safari — automatically fall back to the MediaRecorder API (MP4 or WebM), so MP4 export is available on iOS too via the fallback path. If neither WebCodecs nor MediaRecorder is available, export fails with an unsupported error. This is the finished file for uploading to YouTube, TikTok, etc.
Share HTML — External Mode Not supported on iOS
Small file size. The playback engine loads from kiraneiro.chronovis-software.com at runtime, so internet is required. Engine updates apply automatically. Note: iOS Safari has no way to open a local HTML file in an executable browser context, so this export type is not available on iOS.
Share HTML — Standalone Mode Not supported on iOS
Larger file (~256 KB + project data). The playback engine is fully embedded, so offline playback works. Not dependent on server status. Note: iOS Safari has no way to open a local HTML file in an executable browser context, so this export type is not available on iOS.
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KiraNeiro hosts only the playback engine. You store and manage your content yourself. Publishing means sharing your content — either by sharing a URL pointing to a file in your own storage, or by sending the exported file directly to others.
URL Sharing
Save your JSON + assets to your own cloud storage (like GitHub), then share a URL in the format https://kiraneiro.app/view?src={your-content-URL}. Paste that link on social media and it works as a playback page. We don't generate social media previews (Open Graph) — you add your own thumbnail and caption when you post.
Embedding (iframe)
Embed the playback engine on your own website using <iframe src="https://kiraneiro.app/embed?src={your-content-URL}">. The /embed path shows a minimal control bar.
File Sharing
Send the exported file (.kneiro project file or HTML share file) directly to someone via chat apps, email, or USB drive — no URL needed. The recipient just opens or selects the file in the KiraNeiro viewer to play it locally. This method shares privately with a specific person without publishing anywhere publicly.
CORS Constraints
The viewer fetches your content directly from the URL, so your cloud storage must allow CORS (cross-origin requests). GitHub (Pages and raw file links) works fine, but Google Drive and Dropbox shared links may be blocked by CORS.
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KiraNeiro can be installed as an app (PWA: Progressive Web App).
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How to Record Live Motion Points
Turn on the record button and press play. While playback is running, drag objects on the canvas to record their movement in real time. This is faster and more natural than placing keyframes one by one — your motion syncs with the music.
Recording Confirmation Dialog — 3 Modes
When you stop recording, a dialog offers three options:
Recording Display Timing for Lyrics / Prose
You can also use recording mode to adjust when each line of a lyrics or prose block appears. Turn on the record button, play the project, and click (or tap) the "Next" button at the exact moment you want each line to show. Timing is updated in real time. It feels like tapping along to a beat rather than typing in timecodes.
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Why Won't My BGM Place?
KiraNeiro checks that an audio file's playback duration fits within its placement slot (from its start position to the next BGM item, or to the end of the timeline for the last one). If the file duration is longer than the slot, placement is rejected.
Solution: use a shorter audio file, or shift the BGM start position to widen the slot.
When Does "Update Playback Duration" Appear?
If every object in the project has an endpoint, and the furthest endpoint doesn't match the project's end time, the File menu shows an "Update Playback Duration" option. Click it to set the project end time to the furthest object endpoint. This often happens when you extend objects and forget to adjust the project length.
Unsupported Features (Intentionally Out of Scope)
For information about supported browsers and environments, see the Browser Support section.