# Introduction

> Learn what Blop does, see the four commands that show it working, and choose where to start.

Blop is a local-first OpenTelemetry collector and command-line tool that lets you and your coding agent observe, investigate and verify the software you change.

```bash
blop up --detach                                              # start the collector on 127.0.0.1:27811
OTEL_EXPORTER_OTLP_ENDPOINT=http://127.0.0.1:27811 pnpm test  # run an instrumented workload
blop status --json                                            # check the collector and its store
blop audit --since 15m --json                                 # findings with trace IDs attached
```

The workload must already use an OpenTelemetry SDK: the endpoint variable alone sends nothing. Local collection, queries and audits need no account, API key or model. No instrumented app yet? The [Quickstart](/quickstart/) records sample telemetry with `blop demo`.

## What Blop gives you

- **Standard OpenTelemetry in.** Any OTLP/HTTP exporter, in any language, sends traces and logs to the collector. There is no Blop SDK.
- **Local first.** One process and one store on your machine, listening on `127.0.0.1`. Local collection uploads nothing.
- **Output an agent can parse.** Every query has `--json` output: one document on stdout, bounded results, documented exit codes and no prompts in JSON mode.
- **Evidence, not opinion.** `blop audit` is deterministic and cites trace and span IDs. It reports what was observed together and never claims a cause from correlation alone.

## Choose a Blop path

- [Investigate](/guides/investigate/): drill from collector status to traces, logs and audit findings.
- [Connect a coding agent](/guides/connect-agent/): wire Claude Code, Codex, OpenCode or any MCP client to the collector.
- [Browser checks](/checks/): write a `.blop.ts` file and run it with `blop test` to confirm a user flow works.
- [Blop Cloud](/cloud/): share projects, check runs and organization memory with your team.

To see how these fit together, read [How it works](/how-it-works/).