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LightOnOCR-3-4B

Best OCR model. LightOnOCR-3-4B is the largest and most accurate model of the LightOnOCR-3 family, LightOn's new generation of lightweight end-to-end OCR models with layout and visual understanding. We recommend it for most OCR tasks.

About LightOnOCR-3

LightOnOCR-3 is a new family of highly performant lightweight OCR models. Compared to the previous generation, they bring significant improvements in speed and transcription quality and introduce new visual understanding features: the models now output bounding box coordinates with labels for all visual elements of a document, short descriptions of images, and the numerical data of figures and charts. With these capabilities, they offer a ready-to-use, easier-to-maintain alternative to complex document understanding pipelines.

The models come in three sizes. The 1B keeps the LightOnOCR-2-1B architecture, while the 0.8B and 4B adopt the Qwen3.5 vision-language architecture, which simplifies integration with existing tools and brings a significant speed-up. All models are released under the Apache 2.0 license for research and commercial use.

Highlights

• 📝 Transcription mode: call the model with an empty prompt and get the full page text, as before. Switching from LightOnOCR-2 requires no change
• 📍 Grounding mode: call it with the grounding prompt and every block comes back with a label and a bounding box
• 🖼️ Visual understanding: images get a short description, charts become a table of their data points
• 🧠 End-to-End: one model instead of a document understanding pipeline, easier to deploy and maintain
• 🧾 Versatile: handles tables, receipts, forms, charts, multi-column layouts, and math notation

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Model Variants

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Prompt Modes

The models can be used as before in a transcription-only mode: called with an empty prompt (""; the image only), they output all textual elements of the page as markdown. If you are currently using our previous models, switching to LightOnOCR-3 requires no change, as this is the default behavior.

The new usage mode is to call the models with the grounding prompt. They then output the new vision features alongside the transcribed text. Each block of content is prepended with a placeholder giving its type and its bounding box, in page coordinates normalized to 0–1000:

![title](80,70,920,140)
# Company report 2025

![text](80,175,920,225)
Revenue rose 20%.

![image](80,285,460,545)
A solar-powered factory.

![chart](540,285,920,545)
<table>
  <tr><th>Year</th><th>Revenue</th></tr>
  <tr><td>2024</td><td>€10M</td></tr>
  <tr><td>2025</td><td>€12M</td></tr>
</table>

• Text blocks contain the transcribed content of paragraphs, titles and other text elements.
• Image blocks pair a bounding box with a short description, making visual content accessible to retrieval and question-answering pipelines.
• Chart blocks contain an HTML table of the data points extracted from the figure, turning visual information into structured data.

The placeholder label is one of:

Grounding adds about 25% output tokens over plain transcription (1,433 vs 1,158 tokens per page on average for the 4B). Other instructions are out of distribution: use the empty prompt ("") or grounding.

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Usage with Transformers

Note: LightOnOCR-3-4B loads with the Qwen3.5 classes (Transformers ≥ 5.2, saved with 5.5.4). It is trained and evaluated with thinking disabled, which is the chat template default.

uv pip install "transformers>=5.5.4" pillow pypdfium2

import torch
from transformers import AutoProcessor, Qwen3_5ForConditionalGeneration

model_id = "lightonai/LightOnOCR-3-4B"
model = Qwen3_5ForConditionalGeneration.from_pretrained(model_id, dtype=torch.bfloat16, device_map="auto")
processor = AutoProcessor.from_pretrained(model_id)

url = "https://huggingface.co/datasets/hf-internal-testing/fixtures_ocr/resolve/main/SROIE-receipt.jpeg"
prompt = "grounding"  # or "" for transcription-only

content = [{"type": "image", "url": url}]
if prompt:
    content.append({"type": "text", "text": prompt})
conversation = [{"role": "user", "content": content}]

inputs = processor.apply_chat_template(
    conversation,
    add_generation_prompt=True,
    tokenize=True,
    return_dict=True,
    return_tensors="pt",
    enable_thinking=False,
).to(model.device)

output_ids = model.generate(**inputs, max_new_tokens=1024, do_sample=True, temperature=0.2)
generated_ids = output_ids[0, inputs["input_ids"].shape[1]:]
print(processor.decode(generated_ids, skip_special_tokens=True))

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Usage with vLLM

vllm serve lightonai/LightOnOCR-3-4B \
  --trust-remote-code \
  --default-chat-template-kwargs '{"enable_thinking": false}'

import base64
import io

import pypdfium2 as pdfium
import requests

ENDPOINT = "http://localhost:8000/v1/chat/completions"
MODEL = "lightonai/LightOnOCR-3-4B"
PROMPT = "grounding"  # or "" for transcription-only

# Render the first page of a PDF at 400 DPI, then resize to a longest edge of 2048 px (aspect ratio preserved)
pdf = pdfium.PdfDocument(requests.get("https://arxiv.org/pdf/2412.13663").content)
pil_image = pdf[0].render(scale=400 / 72).to_pil()
pil_image.thumbnail((2048, 2048))

buffer = io.BytesIO()
pil_image.save(buffer, format="PNG")
image_base64 = base64.b64encode(buffer.getvalue()).decode("utf-8")

content = [{"type": "image_url", "image_url": {"url": f"data:image/png;base64,{image_base64}"}}]
if PROMPT:
    content.append({"type": "text", "text": PROMPT})

payload = {
    "model": MODEL,
    "messages": [{"role": "user", "content": content}],
    "max_tokens": 4096,
    "temperature": 0.2,
    "top_p": 0.9,
}

response = requests.post(ENDPOINT, json=payload)
print(response.json()["choices"][0]["message"]["content"])

The LightOnOCR repository on GitHub provides a minimal client, CLI and viewer for the models served with vLLM, plus the code to reproduce our benchmarks.

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Rendering and Preprocessing Tips

• Render PDFs at 400 DPI to images using a target longest dimension of 2048px
• Maintain aspect ratio to preserve text geometry

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License

Apache License 2.0

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Citation

@misc{lightonocr2_2026,
  title        = {LightOnOCR: A 1B End-to-End Multilingual Vision-Language Model for State-of-the-Art OCR},
  author       = {Said Taghadouini and Adrien Cavaill\`{e}s and Baptiste Aubertin},
  year         = {2026},
  howpublished = {\url{https://arxiv.org/abs/2601.14251}}
}