Method

How we score video difficulty

Every number on this site is computed from a video’s actual subtitle track. Nothing is a rating, a vote, or an editor’s impression — which also means every number can be argued with, and this page is where you find the grounds.

What the score means

One number from 0 to 100 that orders content from easiest to hardest to follow. Two cuts divide it into the three shelves used across the site.

One scale, three shelves, the same cuts in every language. Beginner takes only the first fifth of the axis — that is where the calibration put the cut, not a design choice, and it is a fair warning that most of what exists on YouTube is made for people who already speak the language.

The score and the band measure different things

Alongside the score, every video carries a band — A2, N4, HSK4. The band answers “how much vocabulary does this assume?”. The score answers “how hard is this to keep up with?”. A band is never derived from a score, or the reverse.

This is why a band and a score can disagree. The lecture uses harder words, so its band is higher. The vlog is spoken far faster, so it is the one you will struggle to follow — and the score, which is mostly pace, ranks it harder. Both numbers are true; they answer different questions.

Each language uses the framework its learners actually think in: CEFR for English, French and Spanish, JLPT for Japanese, HSK for Chinese. Translating a JLPT level into CEFR would lose more than it explains, so we don’t.

How the score is computed

We read the subtitle track, measure two things about it, and weight them. That is the whole pipeline — there is no model judging content quality and no human in the loop.

Four parts pace to one part vocabulary. Those weights are not a guess. They were fitted against 843 videos whose own titles declare a level — a channel calling its episode “beginner” or “advanced” — across Spanish, Japanese and French, and pace predicted that label far better than vocabulary did in all three. Pace is normalised per language, which is what lets one scale cover writing systems as different as Spanish and Japanese.

Where the numbers stop being trustworthy

A measurement whose limits are published can be argued with; one whose limits are hidden can only be believed or dismissed. These are ours.

Scores compare within a language, not across languages. Word rarity is measured against each language’s own corpus, so a 40 in Spanish is not the same experience as a 40 in Japanese.
Japanese bands read about a level too hard. Deciding which JLPT level a word belongs to needs thresholds on a Japanese word-frequency list, and ours are borrowed from the English calibration, which measures roughly two-thirds of a level harsh. That is why N1 is the most common label here, on videos plainly made for intermediate learners. Trust the score and the ordering; read the Japanese band as one notch pessimistic.
Chinese bands are a placeholder, not a measurement. The same thresholds, fitted properly to HSK’s own word lists, labelled almost every Chinese video HSK6 or above — which would have emptied the beginner shelf for the language with the gentlest content on the site. We kept borrowed thresholds instead, which put most Chinese videos between HSK1 and HSK4. Neither number is calibrated against Chinese ground truth, so use Chinese bands only to compare our videos with each other.
Automatic subtitles carry the machine’s errors into the score. Videos whose track was auto-generated rather than written are marked as such wherever they are listed, so you can discount them yourself.
The sample is a curated set of channels, not a random slice of YouTube. Everything here was measured, but not everything on YouTube was measured.

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