clarity CLAUDE.md

Development guidance for Clarity, an open-source TypeScript library that records user interactions and session replays. The project is a monorepo, meaning several related packages share one repository, with special attention to website performance and bundle size.

In plain words
What is it for?
Working on Clarity's tracking library, data decoder, session-replay viewer, and development tools, including building, testing, and maintaining the shared repository.
Why use it?
It helps contributors avoid slowing down websites or making the library download unnecessarily large while keeping the packages consistent.

Instructions file

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add instructions/microsoft/clarity/claude-md
Clone the repo
git clone --depth 1 https://github.com/microsoft/clarity
Per session 1,626 This file is loaded in full into every session.
When invoked 1,626 The same file — it is already loaded in full.
Security scan A 0 findings. Scan, not verified.
Origin 94% copy Near-identical to another mod in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.01626 $0.01626
Opus 5 $0.00813 $0.00813
Sonnet 5 $0.00325 $0.00325
Haiku 4.5 $0.00163 $0.00163

Measured 3d ago against content hash 436fa64d6262, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

clarity CLAUDE.md scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 3d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

Origin

This is a copy

94% identical to clarity copilot-instructions.md — 4 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

CLAUDE.md · 143 lines

How it starts

The opening of the file, as written. The whole thing — 143 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Clarity Development Guidelines

Repository Overview

Clarity is an open-source TypeScript behavioral analytics library for tracking user interactions and session replays. Monorepo with Lerna/Yarn workspaces:

  • clarity-js (packages/clarity-js): Core instrumentation library
  • clarity-decode (packages/clarity-decode): Data decoder
  • clarity-visualize (packages/clarity-visualize): Session replay visualization
  • clarity-devtools (packages/clarity-devtools): Chrome extension (private)

Stack: TypeScript, Rollup, TSLint, Playwright, Lerna, Yarn workspaces

clarity-js Performance & Bundle Size Priorities

Critical: clarity-js has two top priorities that must guide all development decisions:

  1. Performance - As an analytics library running on diverse websites, clarity-js must not hurt website performance or impact metrics like INP (Interaction to Next Paint) or PLT (Page Load Time). Balance data collection needs with:

    • Avoid blocking the main thread
    • Minimize network requests
    • Reduce payload size
  2. Bundle Size - Small bundle size is crucial for loading clarity-js quickly and starting data collection as soon as possible. Every byte matters.

Build & Development Commands

Installation

ALWAYS run yarn install before building or testing. (~25s, peer dependency warnings are normal)

Building

yarn build              # All packages (~45s, Lerna parallel build)
yarn build:js           # clarity-js only (~20s)
yarn build:decode       # clarity-decode only
yarn build:visualize    # clarity-visualize only
yarn build:devtools     # clarity-devtools only

Rollup + TypeScript → multiple formats (CJS, ESM, IIFE minified). Build artifacts auto-cleaned to build/ or extension/ (gitignored).

Build outputs per package:

  • clarity-js: clarity.js (CJS), clarity.module.js (ESM), clarity.min.js (minified), plus variants: clarity.extended.js, clarity.insight.js, clarity.performance.js, clarity.livechat.js, and dynamic module builds (clarity.tidio.js, clarity.crisp.js)
  • clarity-decode: clarity.decode.js (CJS), clarity.decode.module.js (ESM), clarity.decode.min.js (minified)
  • clarity-visualize: clarity.visualize.js (CJS), clarity.visualize.module.js (ESM), clarity.visualize.min.js (minified)
  • clarity-devtools: Output to extension/ directory for Chrome extension

Read the full file on GitHub · 143 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 3d ago First seen · 143 lines · 1,626 tokens per session scan A 436fa64d6262

Subscribe to this mod's changes

clarity CLAUDE.md is an instructions file published in the GitHub repository microsoft/clarity (2,729 stars, last pushed today), licensed MIT. It adds 1,626 tokens to every session, about $0.0081 per session on Opus 5. A static security scan graded it A with 0 findings. It is 94% identical to clarity copilot-instructions.md, differing in 4 lines, and is treated as a copy.

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