AI Image Caption Generator

What the AI Image Caption Generator does

Give this tool an image and it writes a short, natural-language description of what is in it — for example, 'a brown dog sitting on a grassy field'. It runs the ViT-GPT2 captioning model in your browser via WebAssembly, so your pictures are described locally and never uploaded to any server.

Automatically generated captions are genuinely useful for writing alt text that makes images accessible to screen-reader users, for drafting social-media captions, for adding searchable descriptions to a photo library, and for giving content teams a quick first-pass description they can refine.

How image captioning works

The model has two halves working together. A Vision Transformer (ViT) divides the image into patches and encodes them into a numerical representation of the visual content. A GPT-2 language decoder then reads that representation and generates a sentence word by word, much like predictive text, but conditioned on what the image encoder saw.

Generating a few captions rather than one gives you options, because the decoder can phrase the same scene in slightly different ways. You can pick the wording that fits best, which is often quicker than writing a description from scratch.

How to use it and its limits

Upload an image and let the model run — it downloads once on first use and is cached for instant reuse afterwards. Clear photos of common subjects produce the most accurate captions. Like all captioning models it can occasionally misread an unusual scene, miscount objects or miss fine detail, so treat the output as a strong starting point and edit it before publishing, especially when it will be used as accessibility alt text.