Claude Token Counter by Krishna Somani

Unofficial extension, not affiliated with Anthropic.
Claude Token Counter adds a real-time heads-up display directly on claude.ai so you always know where you stand before hitting a limit.
What it shows:

Approximate token count for the current conversation, with a progress bar against the 200k context limit
Cache countdown timer showing how long your conversation stays cached
Session (5-hour) and weekly (7-day) usage bars pulled from Claude's native API, more accurate than the rounded percentages on Claude's own usage page

How it works:
All data is processed locally in your browser. The extension reads Claude's own API responses to get precise usage fractions and uses a built-in tokenizer to estimate token counts. No data is ever sent to any external server.