> ## Documentation Index
> Fetch the complete documentation index at: https://tbd-6fc993ce-hypeship-docs-ia-v2.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Concurrency and Limits

> How many browsers you can run, how fast you can create them, and what each one gets

Three separate limits shape a scaled workload, and they're easy to confuse. Concurrency caps how many browsers exist at once. The create rate caps how fast you can ask for new ones. Per-browser resources cap what one browser can do.

## Concurrency

One org-wide limit covers every browser you're running, whether created on demand with `browsers.create()` or reserved in a [browser pool](/browsers/pools). The full limit is available to either API in any mix.

| Limit | Developer | Hobbyist | Start-Up | Enterprise |
| - | - | - | - | - |
| Concurrent browsers | 5 | 10 | 150 | Custom |
| App invocations | 5 | 10 | 50 | Custom |
| App invocations (per app) | 5 | 10 | 20 | Custom |
| Managed auth health check interval | 6 hours minimum | 1 hour minimum | 20 minutes minimum | Custom |

Limits are org-wide unless stated otherwise.

Two things count against the concurrent browser limit that people don't expect:

* **Reserved pool capacity counts whether or not it's acquired.** A pool sized to 40 browsers uses 40 of your limit for as long as it exists.
* **Browsers in [standby](/browsers/standby) count.** Standby stops usage charges, not the concurrency slot. Delete the browser to release it.

Set per-project caps if you're splitting one org limit across teams or environments — see [project concurrency limits](/info/projects#concurrency-limits).

## Rate limits

Kernel enforces per-organization rate limits on API requests. Browser creation is rate limited separately from concurrency: the create rate caps how fast you can create browsers, not how many you may run.

Acquiring from a [browser pool](/browsers/pools) isn't subject to the create rate — the pool's browsers already exist. If your traffic arrives in bursts, that's the reason to use a pool even when your concurrency headroom is fine.

### What happens at the limit

Exceeding a rate limit returns `429 Too Many Requests`. Rate-limited endpoints include these headers on every response:

| Header | Description |
| - | - |
| `X-RateLimit-Limit` | Maximum requests allowed per minute |
| `X-RateLimit-Remaining` | Requests remaining in the current window |
| `Retry-After` | Seconds to wait before retrying (only on `429` responses) |

All Kernel SDKs retry a `429` up to 2 times, honoring `Retry-After`. If retries are exhausted, the SDK raises a typed `RateLimitError` carrying the response headers, so you can apply your own backoff. Queue on your side rather than tightening the retry loop: a `429` means the org is over budget for the minute, so retrying faster doesn't help.

If you're hitting the ceiling in normal operation, [contact us](https://calendly.com/d/d3tn-5kp-5yt) — the limit is raisable.

## Per-browser resources

| Resource | Headful | Headless |
| - | - | - |
| Default memory | 8 GB | 1 GB |

Memory is the practical ceiling on how many tabs and how heavy a page one browser handles. A [headless](/browsers/headless) browser at 1 GB is sized for short-lived, single-page, high-concurrency automation; open a dozen heavy tabs in one and Chromium starts killing renderers. If your workload needs many concurrent pages, spread it across more browsers rather than more tabs in one. [Browser pools](/browsers/pools) accept a `memory` setting when a workload needs more than the default.

[GPU acceleration](/browsers/gpu-acceleration) is a separate browser type with its own [usage rate](/info/pricing#usage-rates), available on Start-Up and Enterprise.

## Other limits worth knowing

| Limit | Where |
| - | - |
| Browser `timeout_seconds` (default 60, max 259200 / 72h) | [Termination](/browsers/termination) |
| Pool `timeout_seconds` (default 600) and fill rate | [Browser pools](/browsers/pools) |
| How managed auth health checks run | [Connection lifecycle](/auth/connection-lifecycle) |
| Replay retention, extensions, projects, per plan | [Pricing](/info/pricing#managed-infrastructure) |
| Monthly spend | [Spending caps](/info/spending-caps) |