Two measurements, one answer
What most people think
Open models are hobby projects. The paid ones are a generation ahead, and closing that gap will take years.
What the data shows
4months
Epoch AI, a research group that scores models on hard tests, measures the best open model four months behind the best closed one.
A second measure asks which model people prefer. The closed lead there grew from 0.5% to 3.3%.
Four months behind, and the gap has stopped shrinking.
In plain terms Two panels: on the left what most people assume, on the right what the numbers show, with the one figure that settles it.Source · Epoch AI, open-closed capability gap · May 2026
What the labels actually mean
Four months, then. Three words decide what those four months are worth, and one of them is doing work you did not agree to.
- Open weights
- You get the finished model file to download and run. That is the cake, not the recipe.
- Open source
- Weights plus the code and the data that made them. Almost no large model ships all three.
- ECI
- Epoch AI's capability index. One score from many hard tests, so two models rank on the same scale.
Three months behind, then four
Two readings of the same gap, seven months apart. In between, the day an open model caught April's best closed one.
Three months behind in October 2025. Four months behind in May 2026.
In plain terms The key events in order down a rail, with coloured dots flagging the pivotal moments.Source · Epoch AI data insights and model pages · September 2026
Eight points, spread very unevenly
Eight points ahead on the index, four months ahead in time. Those are two readings of the same gap: the points say how far behind, the months say how long the catch-up took. Only these four tests score both models on the same terms.
Near parity on graduate science. On a puzzle game the open model scores 26% against 84%. Epoch AI warns this reading may understate the gap, because open models are tuned hard on public tests.
In plain terms Each bar is the gap between two scores on one test, the best open model against the best closed one. Longer bar, bigger gap.Source · Epoch AI model pages · September 2026
Not the labs you have heard of
Those gaps run from three points to fifty-eight. So who releases these open models? Three Chinese labs: DeepSeek, Moonshot, which makes Kimi, and Zhipu, which makes GLM. Each has one column below, and a line joins every model to the one built from it.
- deepseek-v3-2 DeepSeek · V3.2 open
- deepseek-v4-pro DeepSeek · V4-Pro, MIT licence open
- deepseek-v4-flash DeepSeek · V4-Flash, MIT licence open
- kimi-k2-thinking Moonshot · Kimi K2 Thinking open
- kimi-k2-6 Moonshot · Kimi K2.6 open
- kimi-k3 Moonshot · Kimi K3, 2.8T open
- glm-5 Zhipu · GLM-5 open
- glm-5-1 Zhipu · GLM-5.1 open
- gpt-5-5 OpenAI · GPT-5.5 closed
- gpt-6-astra OpenAI · GPT-6 Astra closed
Eight of these ten releases are open weights, and the newest landed in July.
In plain terms Each row is one release. A line joins a model to the one built from it, and the colour marks open weights against closed.Source · Epoch AI Benchmarking Hub model pages · September 2026
Free is only the top layer
Eight of those ten releases are free to download. Nothing under them is, so the rest of the stack stays somebody else's bill, and that kharcha does not come with the file.
Training data is almost never released, and the compute to serve a model is not downloadable at any licence.
In plain terms Five slabs, stacked. The top one is what you can download today. Each slab below it is another thing the word open could mean.Source · Stanford HAI, Hugging Face open-model census, AI Now Institute · September 2026
Three prices for the same million tokens
The one layer you can rent has a price. Here it is, per million tokens, which means the small chunks of text a model reads and writes.
GPT-6 Astra, the closed frontier
$50per million output tokens
Ask the same question in an Indian language and it costs about five times the English price.
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The same million from the best open model, $15 Less than a third of the frontier price
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From DeepSeek V4-Flash, $0.28 The cheapest open model on the list
A million output tokens costs $50 from the closed frontier and $15 from the best open model.
In plain terms One number, large, and beside it the everyday things it equals, so the size can be felt rather than read.Source · Epoch AI model pages · September 2026
The offer nobody took
Renting the open model costs less than a third of renting the closed one, and downloading it costs nothing at all. One count of state-backed AI projects found 139, across 56 countries. About 40% picked Llama, Meta's open-weight model. Not one picked a model from the labs actually at the open frontier. Think of a free textbook nobody opens because the shelf sits in another building.
That means the four months is not what keeps people away. The bottom slab of that stack does, the compute to run the model, and no licence makes that part free. Of all downloads, 83% go to models under a billion parameters, the smallest on offer. India's pull is different. Sarvam AI adapts open-weight models to Indian languages, work you can only do when you hold the weights instead of renting them by the token.
Source · Rest of World, Hugging Face open-model census · September 2026
The four months is free. Almost nobody takes it.