Molmo2: Open Weights and Data for Vision-Language Models with Video Understanding and Grounding
Authors: name: Christopher Clark, name: Jieyu Zhang, name: Zixian Ma, name: Jae Sung Park, name: Mohammadreza Salehi, name: Rohun Tripathi, name: Sangho Lee, name: Zhongzheng Ren, name: Chris Dongjoo Kim, name: Yinuo Yang, name: Vincent Shao, name: Yue Yang, name: Weikai Huang, name: Ziqi Gao, name: Taira Anderson, name: Jianrui Zhang, name: Jitesh Jain, name: George Stoica, name: Winson Han, name: Ali Farhadi, name: Ranjay Krishna

Today's strongest video-language models (VLMs) remain proprietary. The strongest open-weight models either rely on synthetic data from proprietary VLMs, effectively distilling from them, or do not disclose their training data or recipe. As a result, the open-source community lacks the foundations needed to improve on the state-of-the-art video (and image) language models. Crucially, many downstream applications require more than just high-level video understanding; they require grounding -- either by pointing or by tracking in pixels. Even proprietary models lack this capability. We present Molmo2, a new family of VLMs that are state-of-the-art among open-source models and demonstrate exceptional new capabilities in point-driven grounding in single image, multi-image, and video tasks. Our key contribution is a collection of 7 new video datasets and 2 multi-image datasets, including a dataset of highly detailed video captions for pre-training, a free-form video Q&A dataset for fine-tuning, a new object tracking dataset with complex queries, and an innovative new video pointing dataset, all collected without the use of closed VLMs. We also present a training recipe for this data utilizing an efficient packing and message-tree encoding scheme, and show bi-directional attention on vision tokens and a novel token-weight strategy improves performance. Our best-in-class 8B model outperforms others in the class of open weight and data models on short videos, counting, and captioning, and is competitive on long-videos. On video-grounding Molmo2 significantly outperforms existing open-weight models like Qwen3-VL (35.5 vs 29.6 accuracy on video counting) and surpasses proprietary models like Gemini 3 Pro on some tasks (38.4 vs 20.0 F1 on video pointing and 56.2 vs 41.1 J&F on video tracking).