YOLOv4 vs YOLOX

YOLOv4 is an object detection model developed by Alexey Bochkovskiy, Chien-Yao Wang, and Hong-Yuan Mark Liao at Academia Sinica, released in April 2020 via the Darknet framework. It combines a CSPDarknet53 backbone, PANet neck, and YOLOv3 detection head with a large set of training improvements — Bag of Freebies and Bag of Specials — that improve accuracy with minimal inference cost increase.

YOLOv4 achieves 43.5% AP on COCO at 65 FPS on a Tesla V100 GPU. The Darknet implementation is the original version, distinguishing it from subsequent PyTorch-based reimplementations. It remains a widely referenced detection architecture and a supported training target in Roboflow Inference.

YOLOX is an anchor-free object detection model developed by Megvii (Face++), released in July 2021 under the Apache 2.0 license. It applies anchor-free detection to the YOLO framework, decoupling the classification and regression heads to allow each to optimize independently, and introduces the SimOTA label assignment strategy for improved training convergence. YOLOX achieves strong accuracy-speed tradeoffs and outperforms YOLOv5 on COCO at comparable model sizes.

YOLOX-L achieves 50.0% AP on COCO at 68.9 FPS on an NVIDIA V100 GPU. The model is available in a range of sizes from YOLOX-Nano to YOLOX-X and supports deployment through ONNX, TensorRT, and other standard export formats. It is suitable for real-time object detection applications and has been widely adopted in industrial and research detection pipelines.