Local tunneling vs a webhook debug workspace
ngrok is a mature localhost tunnel with Traffic Inspector and replay. Mercur starts one step earlier — a guest tunnel that forwards to localhost with no signup — then grows into a persistent local traffic workspace with hosted Remote MCP for IDE agents.
Choose Mercur when you want a public URL forwarding to localhost before you create any account, and a registered Endpoint with request history and hosted Remote MCP waiting in the same product when the project sticks.
Choose ngrok when you need a battle-tested CLI tunnel across platforms, broad protocol coverage, Traffic Inspector in the ngrok dashboard, or an existing team already standardized on ngrok.
How the jobs compare
| Job | Mercur | ngrok |
|---|---|---|
| Public URL for a webhook, first minute | Guest URL from npx, no account | CLI tunnel after install + signup |
| See headers and body in the browser | Console request log | Traffic Inspector (full capture for bodies) |
| Forward to localhost | npx CLI with no account; macOS app optional | CLI on many platforms, after authtoken |
| Persistent free URL | Free registered HTTP endpoint | Free plan includes a static dev domain |
| IDE agent inspect (MCP) | Hosted Remote MCP over OAuth on Solo / Team | MCP gateway to expose your own servers |
| Inbound email testing | Temporary @mercur-mail.com inbox on Solo / Team | Tunnel product, no inbound mailbox documented |
| Linux / CI scripting | npm CLI (@mercur_dev/cli) with --json output | Strong CLI + automation |
Last verified: 3 September 2026. Competitor details change — verify on each vendor’s site.
Where Mercur is stronger
- A tunnel that forwards to localhost before you create an account — one npx command, no authtoken step
- Signing up from the inspector keeps the guest URL and its stored requests
- Hosted Remote MCP so an IDE agent can list endpoints and open payloads
- HTTP, WebSocket, and TCP through one agent (macOS app or npm CLI) on paid plans
- A temporary inbox for signup codes and magic links on Solo and Team
- A revocable 24-hour read-only link when a teammate needs to see the payload
When ngrok wins
- Mature brand and docs that providers already mention
- CLI-first workflows on more than macOS
- Traffic Inspector with replay (full capture is an account setting)
- Broad tunneling beyond webhook-shaped HTTP
- Enterprise trust and checklist breadth Mercur does not claim yet
Common questions
Is Mercur an ngrok alternative?
For webhook debugging and inspect-first endpoints, yes — that is the comparison this page is for. Mercur does not try to replace ngrok as a general network Swiss-army knife.
Does ngrok inspect and replay traffic?
Yes. ngrok Traffic Inspector can view and replay HTTP traffic; full request/response capture is an account setting. Mercur does not claim uniqueness for inspection or replay.
Does Mercur require a CLI?
No CLI is required to catch a payload on the guest webhook inspector — that is a browser URL. Forwarding to localhost needs an agent: either the npm CLI, which runs a guest tunnel without an account, or the macOS desktop app once you register.
Can I tunnel to localhost without creating an account?
Yes. `npx @mercur_dev/cli http 3000` opens a guest HTTP tunnel with no account and no token, prints the public URL, and forwards traffic to that port. It carries guest limits — 1,000 requests per month, the 50 most recent requests stored, and a 24-hour idle lease. ngrok asks you to sign up and add an authtoken before the first tunnel.
Can I keep a stable URL on the free plan?
Registered Free includes one HTTP Endpoint with a stable URL, and signing up from the guest inspector moves that guest URL and its request log into your workspace. A guest URL on its own is ephemeral — a 24-hour idle lease and guest request caps — so it is the right tool for tonight, not for a URL you hand to a provider for months. ngrok’s free plan also includes an auto-assigned dev domain, so a stable free URL is not a Mercur-only capability.
Does Mercur run on Windows or Linux?
The desktop app is macOS. The npm CLI (@mercur_dev/cli) runs on macOS, Linux, and Windows with Node.js 20+. There is no Windows or Linux desktop app.
Can a coding agent start a Mercur tunnel on its own?
Yes. `npx -y @mercur_dev/cli http <port> --json` prints one JSON object with the public URL as soon as traffic can flow, so an agent can read the URL instead of scraping log lines. Guest HTTP needs no token.
Related pages
Mercur vs Hookdeck
Webhook event gateway with ingest, filtering, replay, and CLI MCP — oriented beyond local debug.
Read comparison →Mercur vs webhook.site
Instant payload bin with browser inspect and an email address per token. CLI forward (`whcli`) when you need localhost.
Read comparison →Mercur vs Hooklistener
Webhook URL + inspect product aimed at no-CLI, no-signup debugging (vendor-documented).
Read comparison →Mercur vs Cloudflare Tunnel
Mature edge tunnel with your Cloudflare account and domain — not a webhook console.
Read comparison →Try Mercur on a real webhook
Get a public HTTPS URL and inspect the payload in the browser, or run npx @mercur_dev/cli http 3000 to forward it to localhost without an account. Register when you want a stable endpoint.