TokenCalculator.dev is a 100% browser-based, privacy-first LLM token counter and API cost estimator built for developers. Unlike traditional text-only counters, it runs client-side to calculate tokens and costs from prompts, local documents (PDF, DOCX, and code in 20+ languages up to 12 MB), and image files (PNG, JPEG, WebP, GIF) across OpenAI, Claude, Gemini, and DeepSeek. With exact o200k_base BPE tokenization and calibrated multi-model projections, developers can accurately budget RAG pipelines, prompts, and context windows with zero server uploads.