The paper titled "MM1.5: Methods, Analysis & Insights from Multimodal LLM Fine-tuning" introduces a new family of multimodal large language models (MLLMs) aimed at improving capabilities in various areas such as text-rich image understanding, visual referring and grounding, and multi-image reasoning. This work builds on the previous MM1 architecture and emphasizes a data-centric approach to model training. The authors systematically investigate the effects of diverse data mixtures throughout the model training lifecycle. This includes the use of high-quality Optical Character Recognition (OCR) data and synthetic captions for continual pre-training, as well as an optimized visual instruction-tuning data mixture for supervised fine-tuning. The models developed range from 1 billion to 30 billion parameters and include both dense and mixture-of-experts (MoE) variants. The findings suggest that with careful data curation and training strategies, strong performance can be achieved even with smaller models, specifically those with 1B and 3B parameters. Additionally, the paper introduces two specialized variants of the MM1.5 model: MM1.5-Video, which is tailored for video understanding, and MM1.5-UI, designed for mobile user interface understanding. Through extensive empirical studies and ablation experiments, the authors provide detailed insights into the training processes and decisions that shaped their final model designs. This research offers valuable guidance for future developments in multimodal large language models, highlighting the importance of data quality and training methodologies in achieving effective model performance. The paper was submitted on September 30, 2024, and is categorized under subjects such as Computer Vision and Pattern Recognition, Computation and Language, and Machine Learning. The authors express gratitude for the support received from various institutions and contributors, indicating a collaborative effort in advancing the field of multimodal learning.