CaptchaKrakenV2-CNN-lite

The lite CaptchaKraken v2 element detector: the CPU-friendly sibling of CaptchaKraken/CaptchaKrakenV2-CNN-large. It finds a captcha board's interactive elements (grid, cell, item, draggable, drop_target, slider, text_input, button, click_area, fill, checkbox).

The CaptchaKraken V2 CNN family

The v2 element detectors: they find a board's interactive elements and draw the numbered marks the v2 pointer models (CaptchaKraken/SunlightV2-0.8B, CaptchaKraken/TwilightV2-2B, CaptchaKraken/MidnightV2-4B) read.

Repo	What
CaptchaKraken/CaptchaKrakenV2-CNN-large	detector.onnx (the client's standard CPU detector) and the Mask R-CNN ResNet-18 training checkpoint detector_r18.pt
CaptchaKraken/CaptchaKrakenV2-CNN-lite	detector-lite.onnx, the MobileNetV3 lite CPU detector for one or two vCPUs — this repo

detector-lite.onnx: the lite CPU detector

The same 11 classes on a MobileNetV3-Large FPN (128 channels, GroupNorm, 1024-wide box head), for one or two vCPUs: 80-107 ms a board on one core, against 520-606 ms for detector.onnx. Same ONNX interface; model metadata arch is lite. The client picks it with detector: "lite" in captchakraken.config.json, or under auto on a machine with two usable CPUs or fewer.

• Trained 2026-11-01 from ImageNet weights: 17,274 steps on the 46,065 generated boards (149 generators + checkbox widgets) that detector.onnx in CaptchaKrakenV2-CNN-large was trained on (short side 384-512), then 4,000 steps on the same boards with the checkbox widgets drawn one vendor at a time. Per-class numbers and both runs' settings in detector-lite.onnx.metrics.json.
• Val (4,606 boards): mask mAP@0.5 0.926, box mAP@0.5 0.930; checkbox mask AP50 1.000, draggable 1.000, grid 1.000, cell AP50 0.970.
• Real captures: every reCAPTCHA, hCaptcha, Prosopo and GeeTest grid board read as detector.onnx reads it; 132/132 held-out widget tick boxes found and 42/42 ticked widgets left alone.
• Limit: a box that fills the whole picture is not found. GeeTest v4's "click to verify" bar is that case; the client clicks it through its DOM selector and never asks.

The interface (opset 17; input image, float (3, H, W) in 0-1; outputs boxes, labels, scores, masks; class names in the model metadata classes) is the same as detector.onnx in CaptchaKrakenV2-CNN-large.

Results across the family

License: LGPL-3.0.