> ## Documentation Index
> Fetch the complete documentation index at: https://docs.e2b.dev/llms.txt
> Use this file to discover all available pages before exploring further.

# Frequently asked questions

> Common questions about E2B billing, sandbox limits, templates, storage, networking, and security.

## Account, billing & limits

### How do I calculate the price of a sandbox?

E2B bills per second, only while a sandbox is running, based on the vCPU and RAM allocated to it. Paused and killed sandboxes are not billed. [Read more](/faq/calculate-sandbox-price)

### How do I increase my concurrency limit?

Raise your concurrent sandbox limit with self-serve add-ons in the console billing tab, or contact sales for higher limits on the Enterprise plan. [Read more](/faq/increase-concurrency)

### How long does a sandbox live?

A sandbox is not session-scoped. Continuous runtime is capped by plan (1 hour Hobby, 24 hours Pro, custom Enterprise) and resets on pause and resume, while a paused sandbox is kept indefinitely with no time-to-live. [Read more](/faq/sandbox-lifetime)

### Do paused sandboxes count toward the concurrency limit?

No. Only running sandboxes count toward the concurrency limit and only running sandboxes are billed. There is no time limit on how long a sandbox can stay paused. [Read more](/faq/paused-sandboxes-concurrency)

### Does E2B support GPUs?

No. E2B sandboxes are CPU-only, sized by vCPU and RAM only, with no GPU option in the SDKs, CLI, API, or a template definition. BYOC does not change this. [Read more](/faq/gpu-support)

## Templates & builds

### What limits apply to my template builds?

Two kinds of limit apply: plan limits like concurrent builds can be raised by upgrading or contacting support, while build timeouts are fixed for everyone and require restructuring the build. [Read more](/faq/build-limits)

### Is there a limit on how many templates I can create?

No. There is no limit on the total number of templates. The only template limit is on concurrent builds: 20 on Hobby and Pro, custom on Enterprise. [Read more](/faq/template-limit)

### Can I make a template public so other projects can use it?

Yes. Publish a template from the console Templates tab or with the CLI, and any project can then create sandboxes from it by its full project-slug/template-name. [Read more](/faq/public-templates)

### Why does pip install fail when building a template?

Large packages like PyTorch with CUDA exhaust the build environment: pip caches wheels in memory (`MemoryError`) and downloads them to the RAM-backed `/tmp` capped at \~3.9 GB ("No space left on device"). Set `TMPDIR` to a disk-backed path with `--no-cache-dir`, or install CPU-only builds. [Read more](/faq/pip-install-error)

### Why does my template build fail with a Docker push authentication error?

Docker sends no credentials to the build registry. Add E2B's local registry proxy (`host.docker.internal:49984`, or `localhost:49984` on Linux) to Docker's insecure-registries and restart Docker. [Read more](/faq/docker-push-authentication-error)

## Storage & volumes

### What are the limitations of the Volumes beta?

File locking can hang, file metadata caching is disabled, read/write permission bits are not enforced between users, mounts are fixed at sandbox creation, and snapshots and read-only mounts are not yet supported. [Read more](/faq/volumes-beta-limitations)

## Networking & deployment

### Can I run sandboxes in the EU?

Yes. E2B offers a shared EU cluster for customers on the Pro tier and above. Contact support to get access. [Read more](/faq/eu-region)

### Do you publish egress IP ranges (CIDRs)?

No. Sandbox outbound traffic leaves from ephemeral, rotating IPs, so there is no fixed E2B-owned CIDR list. Allowlist the cloud provider's published ranges or route sandbox traffic through your own proxy for a dedicated IP. [Read more](/faq/egress-ip-ranges)

### Why does iptables fail with 'xt\_owner module missing' in a sandbox?

The E2B sandbox kernel does not ship the `xt_owner` module, so iptables rules using `--uid-owner` or `--gid-owner` fail. Use nftables, which does not need `xt_owner` for owner-based matching. [Read more](/faq/iptables-xt-owner)

### Why does my custom template fail with 'port 49999 not open'?

The Code Interpreter service inside the sandbox did not start, usually because the custom template was not built on the `code-interpreter-v1` base or the start command is missing. [Read more](/faq/port-49999-not-open)

## Security & compliance

### Is E2B SOC 2 compliant?

Yes. E2B has a SOC 2 Type II report, served with the DPA template, penetration test, and bridge letter from the Trust Center at [trust.e2b.dev](https://trust.e2b.dev). [Read more](/faq/security-and-compliance)

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