How to make a preview sheet for stock footage submissions
- Step 1Check the library's preview spec — Confirm what the stock site asks for: grid count (often 4x4), file type (this tool outputs PNG), and any max pixel dimensions. Set the tool's controls to match before generating.
- Step 2Drop your clip onto the tool — Drag the MP4, MOV, MKV, WebM, or AVI you are submitting onto the upload zone. It is processed locally via FFmpeg.wasm and never uploaded — important for clips you have not yet licensed.
- Step 3Set Columns and Rows to the required grid — 4x4 (16 frames) is the typical ask. If the library wants more or fewer cells, set accordingly — each accepts 1-10, so anything from a 1xN strip to a 10x10 is possible.
- Step 4Set Tile width to hit dimension limits — If the library caps the sheet's pixel size, work backward: final width is roughly
columns x tile width. Lower the tile width to stay under the cap; raise it for a sharper sheet within limits. - Step 5Generate the preview sheet — Run it. The tool probes duration, samples one frame per equal interval, and tiles them into one clean PNG with no overlays. Verify it matches the spec before uploading to the library.
- Step 6Submit the PNG — Download
<yourfile>-grid.pngand attach it to your submission alongside the clip. For a separate hero/thumbnail still, use thumbnail-extractor.
Matching common submission specs
Typical stock-preview requirements and how to set the tool. Always confirm the exact spec per library.
| Requirement | Set in the tool |
|---|---|
| 4x4 contact sheet | Columns=4, Rows=4 (16 frames) |
| Denser preview (e.g. 5x5) | Columns=5, Rows=5 (25 frames) |
| Max sheet width cap | Lower Tile width so cols x tile width stays under the cap |
| PNG file type | Always — output is PNG by default |
| Clean (no watermark) preview | Default — the tool adds no overlay or logo |
Output dimension reference (PNG)
Approximate final width by grid and tile width. Final width is roughly columns x tile width plus minor tile spacing.
| Grid | Tile width | Approx PNG width |
|---|---|---|
| 4x4 | 320px | ~1280px |
| 4x4 | 640px | ~2560px |
| 5x5 | 320px | ~1600px |
| 6x6 | 240px | ~1440px |
Tier limits for video tools
Most stock clips are short and fit Free easily. No duration cap.
| Tier | Max file size | Files per batch |
|---|---|---|
| Free | 1 GB | 1 |
| Pro | 10 GB | 5 |
| Pro + Media | 100 GB | 50 |
| Developer | 100 GB | Unlimited |
Cookbook
Submission recipes for the most common stock-library preview requirements.
Standard 4x4 preview sheet
The most-requested format. A 4x4 at 320px gives 16 evenly-spaced frames in a tidy ~1280px PNG.
Options: Columns=4 Rows=4 Tile width=320 Frames=16 Output: clip-grid.png (~1280px wide, no watermark)
Fit a max-width cap of 2000px
If the library caps the preview at 2000px wide and wants a 5x5, work the tile width back from the cap.
Target: <= 2000px wide, 5 columns 2000 / 5 = 400 -> use Tile width 400 Options: Columns=5 Rows=5 Tile width=400 Output: ~2000px-wide PNG
Vertical (9:16) stock clip preview
Vertical clips tile with tall cells. A 4x4 still works; the overall sheet is taller than wide.
Options: Columns=4 Rows=4 Tile width=300 Frames=16 (each tall, aspect preserved) Output: a vertical-format preview sheet
Sharper sheet for a high-end clip
For premium footage where reviewers scrutinise quality, raise tile width while keeping a 4x4.
Options: Columns=4 Rows=4 Tile width=640 Frames=16 Output: ~2560px-wide, detailed preview
Preview sheet plus a separate hero still
Some submissions want both a contact sheet and a single thumbnail. Generate the sheet here, the hero still separately.
1. frame-grid-maker (4x4) -> preview sheet PNG
2. thumbnail-extractor -> single hero still
/video-tools/thumbnail-extractorEdge cases and what actually happens
Library requires JPEG, not PNG
Format mismatchThis tool only outputs PNG. If a library strictly requires JPEG for the preview, convert the PNG afterward with an image tool. The grid generation itself is always PNG.
Sheet exceeds the library's max dimensions
Rejected by libraryIf your grid x tile width is larger than the library's cap, the submission may be bounced. Lower the tile width so columns x tile width stays under the limit before generating.
Expecting a watermark or contributor ID on the sheet
Not supportedThe tool adds no watermark, logo, or text. That is usually what stock previews want, but if a library requires an ID stamp, add it afterward in an image editor.
Clip duration cannot be read
ErrorIf the file lacks usable duration metadata, the tool throws "Could not determine video duration" and no sheet is produced. Re-export a clean MP4/MOV and retry.
Very short clip, dense grid
ExpectedA 10x10 on a 6-second stock loop samples nearly identical frames. For short loops use a smaller grid (3x3 or 4x4) so the preview shows real variation.
Letterbox bars in the clip
PreservedBaked-in black bars appear in every tile; the tool does not crop. Crop with video-cropper before generating if you want a clean, bar-free preview.
Columns/rows above 10
ClampedEach dimension caps at 10, so 10x10 = 100 is the densest grid. Requests above 10 are reduced. Most libraries ask for far fewer cells anyway.
Tile width outside 120-1280
ClampedThe panel limits tile width to 120-1280px. Values below or above are clamped, which can affect whether you hit a library's exact dimension spec — plan within that range.
One clip per submission run
Single file onlyThe tool processes one video at a time. For a batch of stock clips, generate a preview sheet per clip in turn.
Aspect ratio differs from the library's expected thumbnail
PreservedEach tile keeps the source aspect, so a vertical clip yields a tall sheet. If a library expects a fixed sheet shape, choose a grid (columns vs rows) that approximates it, since cell shape follows the source.
Frequently asked questions
What grid do stock libraries usually want?
A 4x4 (16-frame) contact sheet is the most common request, but always check the specific library — some want a denser grid. Set Columns and Rows to match; each accepts 1-10.
Does the tool add a watermark or contributor ID?
No. The sheet is a clean mosaic with no watermark, logo, or text. That is what most previews want; if a library needs an ID stamp, add it in an image editor afterward.
What file type is the preview?
PNG only, named <yourfile>-grid.png. If a library strictly requires JPEG, convert the PNG with an image tool after generating.
How do I keep the sheet under a max-width limit?
Final width is roughly columns x tile width. Divide the library's max width by your column count to get the tile width to use. For example, a 2000px cap with 5 columns means a 400px tile width.
Will my unlicensed clips be uploaded?
No. Everything runs in your browser via FFmpeg.wasm. Clips you are preparing to license never leave your machine.
How are the preview frames selected?
By equal time intervals across the whole clip, so the sheet fairly represents the footage rather than just one moment — which is what reviewers want to assess.
Does it handle vertical and square stock clips?
Yes. Each tile preserves the source aspect ratio, so 9:16 and 1:1 clips preview correctly. The overall sheet shape follows the cell shape.
What input formats can I submit from?
MP4, MOV, MKV, WebM, and AVI. The tool reads the container and samples the video stream without re-encoding the source clip.
How big a clip can I process?
Free allows up to 1 GB per file, which covers virtually all stock clips. Pro is 10 GB, Pro + Media and Developer 100 GB. There is no duration limit.
Can I make both a contact sheet and a hero thumbnail?
Yes — generate the sheet here, and pull a single hero still with thumbnail-extractor. Some submissions ask for both.
Why does my 4x4 of a short loop look repetitive?
A short loop has little change between samples, so the 16 frames look similar. That is accurate for the clip; you can drop to a 2x2 or 3x3 for a tidier short-loop preview.
Can I remove black bars before generating?
Yes. If the clip has baked-in letterboxing, crop it first with video-cropper so the preview frames are bar-free.
Privacy first
Every JAD Video tool runs entirely in your browser via WebCodecs and FFmpeg (WebAssembly). Your video files never leave your device — verified by zero outbound network requests during processing.