Thumbnail Lab

Create and refine YouTube thumbnails without leaving the conversation. Give your AI assistant a video title plus 1–3 reference thumbnails whose style you want to match, get a finished thumbnail back in chat, then keep editing it in plain language — "make the text yellow", "swap the background for a city at night".

These are the same generations and edits as the Thumbnail Lab in your NexLev dashboard — same account, same allowance, and everything you make in chat shows up in your Lab history.

Prerequisites

Connected AI assistant — Claude, ChatGPT, or any other supported platform
Signed in with your NexLev account (OAuth) — Connect to your AI assistant
Lite, Pro, or Premium plan — Free plans do not have access. Upgrade your plan to get started.

OAuth login required. Thumbnail Lab tools act on your personal Lab workspace, allowance, and billing, so they are not available on API-key connections. Connect via OAuth to use them.

Your AI assistant calls these tools automatically. Just describe the thumbnail you want in plain language — it handles references, polling, and edits for you.

How It Works

Generate

Give your assistant the video title and 1–3 reference thumbnails whose style you like. It can pull references automatically from NexLev's research tools — for example the thumbnails of outlier videos in your niche via Trending Videos or YouTube Tools.

Optionally add creative direction ("use a red arrow", "dark background"), a short script summary for extra context, or ask for a text-free image.

Wait a moment

Generation returns a jobId immediately and your assistant polls it for you — jobs typically finish in 30–90 seconds. The finished thumbnail is shown right in the chat (in ChatGPT it appears in an interactive preview with Copy URL / Download buttons).

Refine

Ask for changes in plain language. Each edit returns a new version, and you can keep editing the same thumbnail round after round. You can also edit any past generation, or any image by URL.

Tools

`generate_thumbnail`

Generates a brand-new thumbnail from your video title plus 1–3 reference thumbnails whose style should be matched. Returns a jobId immediately — your assistant then polls get_thumbnail_generation_status until the image is ready.

Best for:

"Make me a thumbnail for this video title"
"Match the style of the top videos in my niche"
"Give me a textless thumbnail I can add my own copy to"
"Try the same title in a darker, higher-contrast style"

Example prompts:

Generate a thumbnail for my video "I Tried Waking Up at 4AM for 30 Days" — match the style of the top productivity channels

Find the 3 highest-outlier videos in the personal finance niche and use their thumbnails as style references for my video "I Saved $10,000 in 90 Days"

Generate a thumbnail for "The Truth About AI Coding Tools" using a dark background and a red arrow, based on this reference: https://i.ytimg.com/vi/dQw4w9WgXcQ/maxresdefault.jpg

Generate a no-text thumbnail for my video "5 Hidden Gems in Japan" so I can add my own headline later

Use the pro model to generate a thumbnail for "My $50,000 Home Studio Tour"

Parameters:

Parameter	Type	Description
`newVideoTitle`	string	Required. Title of the video the thumbnail is for
`referenceThumbnailURLs`	string[]	Required. 1–3 HTTPS URLs of reference thumbnails (JPEG/PNG/WEBP/GIF, max 2 MB each)
`referenceThumbnailTitles`	string[]	Video titles of the references, in the same order — optional, but improves results
`generationInstructions`	string	Creative direction, e.g. `"use a red arrow"`, `"dark background"` (max 2000 chars)
`newVideoScript`	string	Script or summary of the video for extra context
`generationMode`	enum	`classic` (full AI thumbnail with text, default) or `no_text` (textless image)
`imageModel`	enum	`pro` (highest quality, Pro plan only), `lite` (fast), `gpt-image-2` (OpenAI, Pro plan only) or `gpt-image-2-low` (OpenAI budget tier, all plans). The GPT models are generation-only. Defaults to the best model your plan allows
`aspectRatio`	enum	`16:9` (default, YouTube), `9:16` (Shorts/Reels/TikTok), `1:1` (square) or `4:5` (portrait)
`outputResolution`	enum	`1K` (default), `2K` or `4K`. The `lite` model supports `1K` only; higher tiers carry a pay-as-you-go surcharge

Reference thumbnails drive the style. YouTube thumbnail URLs follow the pattern https://i.ytimg.com/vi/<videoId>/maxresdefault.jpg, so you can point your assistant at any video — or better, ask it to find outlier videos in your niche first and reuse their thumbnails as references. Passing referenceThumbnailTitles alongside them helps the model understand what each reference was selling.

Image Models

Model	Description	Available on
`pro`	Highest quality	Pro plan
`lite`	Fast	All Lab plans

If you don't pick a model, you automatically get the best one your plan allows.

Example Workflows

Niche-matched thumbnail from scratch

Find the 3 highest-outlier videos in the "AI tools" niche from the last 30 days, then generate a thumbnail for my video "I Replaced My Whole Workflow With AI" in their style

Your assistant finds the outlier videos, reuses their thumbnails as references, generates, polls, and shows you the result.

Iterate to a final cut

Generate a thumbnail for "The Only Budget Video You Need" based on these two references, then make the text yellow, then swap the background for a plain dark gradient

Each round is a separate edit on the same Lab document — you keep every intermediate version.

Rework an existing thumbnail

Take the thumbnail from this video and change the headline to "IT GOT WORSE": https://www.youtube.com/watch?v=dQw4w9WgXcQ

A/B variants for one title

Generate two thumbnails for "I Quit My Job After 9 Years" — one with a dark high-contrast style and one bright and colorful

Included Allowance

One shared allowance across chat and the dashboard — a generation from your AI assistant counts exactly the same as one made in the web Lab.

Plan	Generations	AI edits
Free	— (not available)	— (not available)
Lite	3 / day · 10 / month	3 / day · 15 / month
Pro	5 / day · 25 / month	5 / day · 25 / month

Thumbnail Lab is available on Lite, Pro, and Premium plans only — Free plan users do not have access.

Beyond Your Allowance (pay as you go)

With usage credits enabled in your NexLev account you can keep working after your included allowance runs out — and on non-PRO plans, the pro-tier models (pro, gpt-image-2) are billed entirely from credits without touching your included allowance. Base rates (1K output; 2K/4K generations add a small surcharge):

Action	Lite model	Pro model	GPT Image 2	GPT Image 2 Low
Generation	$0.09	$0.16	$0.12	$0.07
AI edit	$0.07	$0.14	—	—

You're always told the price before an over-allowance action is charged.
Failed jobs are refunded automatically — you only pay for thumbnails that actually complete.
Pay-as-you-go usage is capped at 30 generations and 30 edits per rolling hour.

Without usage credits enabled, the tools simply stop at your included allowance and tell you when it resets.

Troubleshooting

"This tool requires an OAuth connection"

Thumbnail Lab is unavailable on API-key connections. Reconnect your assistant with a NexLev account sign-in — see the Quickstart.

Reference thumbnail rejected

References must be HTTPS URLs pointing at a JPEG, PNG, WEBP, or GIF under 2 MB. If a maxresdefault.jpg URL 404s, that video has no max-res thumbnail — try hqdefault.jpg instead.
You need at least 1 and at most 3 references.

Job stuck on processing

Generations and edits normally finish in 30–90 seconds. Your assistant polls for up to 5 minutes; if it times out, ask it to check the status again with the same jobId.

Job failed

Failed jobs are refunded automatically — no allowance or credits are consumed. Try again, and simplify very long generationInstructions if it keeps failing.

pro model rejected

The pro and gpt-image-2 models are Pro-plan only (gpt-image-2-low is open to every plan). Omit imageModel and you'll get the best model your plan allows. The GPT models can generate but not edit.

Edited image is missing my manual layers

Expected. AI edits act on the base image; layers you added in the web editor are preserved in the Lab but not baked into the image returned in chat.

Allowance reached

Enable usage credits in your NexLev account to keep going past your included allowance, or wait for the reset your assistant reports. Upgrade to Pro for a larger included allowance.

What's Next?

Trending Videos — Find the outlier videos whose thumbnails make the best style references
Similar Thumbnails — Search thumbnails visually across millions of YouTube videos
Swipefile — Save the thumbnails and videos you want to model
Channel Analytics — Study the channels behind the styles you're matching
Niche Overview — Understand the audience you're designing for