Disclosure: we make ThumbnailPeak. We describe ThumbMagic's rater as we found it on 21 October 2026, and we say where it does things we don't.
ThumbMagic is an AI thumbnail maker, and it has a free YouTube Thumbnail Rater. You upload a thumbnail, and it gives you a score out of 100 built from four measurements: contrast, faces, text readability and "color pop". It takes 10 thumbnails a day, with no account.
ThumbnailPeak's thumbnail rater also scores a thumbnail out of 100. It rates seven things about the picture and three about how well it fits your title, and then lists what to fix first.
We gave both tools the same four thumbnails and the same title on the same day. Here is what we found:
- ThumbMagic's text score was backwards. It gave 83 for text to a thumbnail with no words on it, and 27 to one with a big, bold two-word headline.
- ThumbMagic marked all four down for having no face, on a go-kart build video, where the kart is the point. Every result carried the same line: "Needs improvement -- no clear face focal point".
- ThumbnailPeak read what was in each picture. It quoted the headlines and named the parts. Its fixes were specific to each thumbnail, down to the words to put on one of them.
- Both tools put the same thumbnail last, and neither noticed its real problem. Its headline says "2 SEATS", but the picture shows one seat.
How we tested
We used four thumbnails for one video: DIY PRO's "$20 Rust Bucket into Kick $$$ Go Kart W/ Harbor Freight 212", which DIY PRO published under a Creative Commons licence.
- DIY PRO's own thumbnail, the one the video went out with: the rusty frame in the grass, a pink arrow, and the finished green kart. It has no words on it.
- Three concepts made by ThumbnailPeak's generator for the same video in September: "RUST → GREEN", "212 POWER" and "2 SEATS". We wrote in that post that "2 SEATS" was the weakest, "since it says two seats and shows one".
All four files were made the same way, from the 576-pixel copies we published in September, scaled up to 1280×720. So neither tool saw a sharper version of one thumbnail than the others.
ThumbMagic's rater has a field for the video title and one for a target keyword. ThumbnailPeak's has fields for the title and the description. All of them are optional. Each time, we typed the video's real title, "$20 Rust Bucket into Kick $$$ Go Kart W/ Harbor Freight 212", and left everything else blank.
We used ThumbMagic without signing in, and ThumbnailPeak on our own account. A free ThumbnailPeak account includes 2 critiques a month, so repeating all four on a free account takes two months.
The scores
The two tools agree on one thing. "2 SEATS" comes last on both, 42 on ThumbMagic and 83 on ThumbnailPeak.
They disagree about everything else. ThumbMagic's FAQ says a score above 70 "indicates strong thumbnail fundamentals", and none of the four reached it. That includes the thumbnail DIY PRO actually published, on a video that has passed 680,000 views since July 2024. Views don't prove a thumbnail is good, but if a rater says "needs improvement", it should be able to say what needs improving. ThumbnailPeak rated three of the four Exceptional, and "2 SEATS" Strong.
The numbers matter less than the reasons behind them, so here they are.
What ThumbMagic measured
ThumbMagic's result is an overall score, four bars and up to four suggestions. Here are two of the four results, side by side.
The text scores are backwards. DIY PRO's thumbnail has no words at all, and it got Text 83 with "Text reads clearly: Typography remains legible at feed scale". "2 SEATS" has two words in big, heavy yellow letters with a black outline. It got Text 27 with "Use fewer words, heavier weight, and higher contrast". The answer our browser got back from ThumbMagic's server went further: "Very little text detected. Adding 3-5 bold words can boost click-through rates."
It wants a face on every thumbnail. All four results carry the same line: "Needs improvement -- no clear face focal point". Faces scored 15, 36, 0 and 0. None of the thumbnails has a face in it, and a go-kart build doesn't need one: what people click for is the kart. Yet "RUST → GREEN", two kart frames on the grass, got 36 for faces. The server's answer for it reported four faces.
It called the brightest palette muted. "212 POWER" got Color Pop 45 and "Muted color palette: Introduce one high-saturation accent color". Its frame is neon green and its "POWER" is bright yellow, on a dark background.
Nothing in the results is about this video. The suggestions are the same few sentences in different combinations: "Strong contrast", "No clear face detected", "Text reads clearly" or "Low text readability". None of them names anything in the picture: not the kart, the engine, the seat or the arrow. We typed the title every time, and the page says the title lets the rater "evaluate text relevance and keyword alignment". None of the four results mentions the title. The AI Tools panel under each result offered one tool, Generate Optimized Titles, and a button to ThumbMagic's thumbnail maker. We didn't see the "thumbnail improvement prompt" that the page describes.
The page calls it AI. Its server calls it a heuristic. The page says the rater "uses AI-powered image analysis". The answer our browser got back from ThumbMagic's scoring server describes its own method as "scoring_method": "heuristic". We ran two of the thumbnails a second time and got exactly the same numbers. That fits fixed formulas measuring the pixels, not a model looking at the picture. ThumbMagic's own FAQ is candid about what that's worth: "Think of the score as a technical quality check."
What ThumbnailPeak's critique said
ThumbnailPeak's critique rates ten things from 0 to 4: seven about the picture, judged at YouTube's feed sizes down to the 168×94 sidebar, and three about how the thumbnail works with your title. Each rating comes with the reasons behind it, and the report opens with what to fix first.
Here is the report for "2 SEATS", the thumbnail ThumbMagic marked down for its text.
It read the headline correctly: legibility 4 out of 4, because "the large yellow '2 SEATS' headline is clear and readable in the 168×94 rendition". It marked the thumbnail down for something else. The seat, the floating frame, the steering wheel, the hands and the arrow all compete for your eye. Its two fixes say what to change: make the finished kart the one big thing, and give the green frame a background it doesn't blend into.
For "RUST → GREEN", the fix ties the picture to the title:
"RUST → GREEN" describes the paint job. The title promises a $20 kart with a Harbor Freight 212 engine. So the critique suggests words that carry the title's promise, "$20 GO-KART" or "212cc SWAP", and suggests keeping the before-and-after picture.
The other two reports go the same way:
- "212 POWER" scored 93, and its one fix is about the promise too: "The frame is incomplete and does not show the finished result promised by 'into Kick $$$ Go Kart.'"
- DIY PRO's own scored 92. It understood why the thumbnail has no text: "No small headline or critical text needs to be read." Its one fix says fine details "look soft at feed size". That one is our doing, and the critique was right: we had scaled a 576-pixel copy up to 1280×720.
Every rating and its reasons are public: DIY PRO's own, RUST → GREEN, 212 POWER and 2 SEATS.
What neither tool caught
"2 SEATS" says two seats and shows one. ThumbMagic's four measurements don't cover what a picture shows, so it was never going to catch that. ThumbnailPeak should have, and it didn't. Its subject-clarity rating says "The image clearly shows a two-seat go-kart build." It seems to have taken the headline's word for it.
It still put "2 SEATS" last, but for clutter, not for the claim. So a critique doesn't replace your own look: read your headline against your picture before you publish. A thumbnail that promises something the video, or the picture itself, doesn't show is the kind of mistake that costs you viewers after the click.
One more thing to know about ThumbnailPeak's scores: three of these four came within a point of each other, at 92, 92 and 93. A critique tells you whether a thumbnail is ready and what to fix. To choose between two that are both ready, use Compare, which puts them side by side and says which one wins and why.
What ThumbMagic does better
- It's free in volume. 10 ratings a day, with no account. A free ThumbnailPeak account gets 2 critiques a month.
- It's quick. Its page says results appear "within a few seconds". A ThumbnailPeak critique took 13 to 19 seconds each in our test.
- It doesn't keep your image. ThumbMagic's FAQ says the image "is processed in memory and is not stored permanently". ThumbnailPeak keeps a 1280×720 copy of each thumbnail it critiques, which is what Improve works from.
- It suggests titles. Its Generate Optimized Titles tool writes title ideas from your title and keyword. ThumbnailPeak rates how a thumbnail fits your title, but doesn't write titles.
If you want a quick check of contrast before you export, ThumbMagic's Contrast bar gives you one for free. Just don't read its Text or Faces scores as a verdict on your thumbnail.
Feature by feature
Here is what each offers as of 21 October 2026. ThumbMagic's side comes from using its rater and reading its rater page.
- What it scores. ThumbMagic: contrast, faces, text readability and colour pop, combined into one score out of 100. ThumbnailPeak: seven ratings of the picture (legibility, hierarchy, subject clarity, contrast, curiosity value, distinctiveness, and trust and polish) and three of its fit with your title (topic match, promise consistency and title complementarity), combined into one score out of 100.
- Why it gave each score. ThumbMagic: a bar per measurement and a set of general suggestions. ThumbnailPeak: the reasons behind every rating, written about your thumbnail, with what to fix first, in order.
- Your title. ThumbMagic: an optional title and keyword, which none of our four results mentioned. ThumbnailPeak: an optional title and description, scored as three of the ten ratings.
- Fixing it. ThumbMagic: a button to its thumbnail maker. ThumbnailPeak: Improve makes a new version with the fixes you tick, or a change you type, then scores it so you can see whether it helped (1 a month on a free account).
- Choosing between two. ThumbMagic: run each one separately and compare the numbers. ThumbnailPeak: Compare judges two thumbnails side by side and names the winner (1 a month on a free account).
- Seeing it in a feed. ThumbMagic has a separate previewer tool. ThumbnailPeak's thumbnail tester shows your thumbnail among the real YouTube videos for your topic. It's free, with no account and no limit.
- The same image twice. Both give the same result for the same image. On ThumbnailPeak, a repeat of the same image and title brings back the stored report and costs nothing.
- Files. ThumbMagic: JPG, PNG or WebP, up to 5 MB. ThumbnailPeak: up to 50 MB, in any shape at least 640 pixels wide, fitted to 16:9.
- Price. ThumbMagic's rater: free, 10 a day, with no account. ThumbnailPeak's critique: a free account, which comes with 2 critiques, 1 comparison and 1 improve a month.
The takeaway
ThumbMagic's rater is fast and free, and it measures pixels: how strong the contrast is, how saturated the colours are, and whether it can detect a face or text. On our four thumbnails, the last two were wrong on half of them. It read text where there was none and called a big, bold headline hard to read. It counted four faces in a picture of two kart frames, and asked for a face on every thumbnail. None of its advice was about the thumbnails we gave it.
ThumbnailPeak's critique looks at the picture: what's in it, what its words say, and whether it delivers what the title promises. Its fixes named the parts of each thumbnail and the words to put on one of them. It missed that "2 SEATS" shows one seat, so read your own headline against your picture. But if you want to know what to change about a thumbnail before you publish it, it's the rater that will tell you.
Critique your thumbnail with a free account, and see what it says about yours.
We tested ThumbMagic's YouTube Thumbnail Rater and ThumbnailPeak's Critique on 21 October 2026, ThumbMagic in Chrome on a desktop without signing in. The quotes from ThumbMagic come from its rater page, its results and its server's answers to our browser that day, and may have changed since. All four thumbnails were made from "$20 Rust Bucket into Kick $$$ Go Kart W/ Harbor Freight 212" by DIY PRO, published under the Creative Commons Attribution licence (CC BY 3.0). The first is DIY PRO's own thumbnail; the other three were made by ThumbnailPeak's generator from the video, and DIY PRO did not make or approve them. All four were scaled from 576×324 to 1280×720 for this test. ThumbnailPeak is not affiliated with ThumbMagic or DIY PRO.
