How to switch from E2B to Runtime by changing one import

Replace from "e2b" with from "withruntime/e2b" (Python: from withruntime.e2b import Sandbox) and set RUNTIME_API_KEY.

Code written for E2B's SDK runs on Runtime unchanged apart from the import, and the same job costs 77% less. 1,000 one-minute runs of a 2 vCPU, 4 GiB sandbox cost $0.64 on Runtime against $2.76 at E2B's published rates, checked 23 September 2026 (Runtime vs E2B). Both run each sandbox in a Firecracker microVM with its own kernel, so isolation is the same kind.

The change

Terminalnpm install withruntime      # or: pip install withruntime (0.4.0 or later)

TypeScriptimport { Sandbox } from "withruntime/e2b"; // was: from "e2b"

Pythonfrom withruntime.e2b import Sandbox  # was: from e2b import Sandbox

E2B's code interpreter package swaps the same way: withruntime/e2b/code-interpreter in JavaScript and withruntime.e2b.code_interpreter in Python.

Then give the process a key. Locally, any npx withruntime command connects the machine with one browser approval and the SDK finds that connection by itself. On a server or in CI, set RUNTIME_API_KEY from your secret manager: make one at API keys or with npx withruntime keys create --name app.

Test it on the free trial first

While you test, keep the work on the 50 free trial hours so nothing touches paid credit:

TypeScriptimport { Sandbox } from "withruntime/e2b";const sbx = await Sandbox.create({ runtime: { create: { funding: "trial" } } });const result = await sbx.commands.run("python3 -c 'print(6 * 7)'");console.log(result.stdout);await sbx.kill();

Pythonfrom withruntime.e2b import Sandboxsbx = Sandbox.create(runtime_create={"funding": "trial"})print(sbx.commands.run("python3 -c 'print(6 * 7)'").stdout)sbx.kill()

Remove the funding option when you go live, once credit is on the account.

What stays the same

What throws, and why that is safe

A call Runtime handles differently, such as E2B templates, workload identity or a single lease over an hour, throws NotSupportedError before anything happens, and the message names what to use instead, so nothing half-runs. E2B.md in the package lists every mapping.

Two common replacements:

• Templates become custom images: a package list, any public or private image, or a Dockerfile, built once.
• Sessions over an hour become a lease you extend, or persistent: true on a paid account, which renews itself while credit lasts.

When to port to Runtime's own calls

The import keeps your code running today. Moving to withruntime itself opens what E2B's API has no call for: exec that returns exitCode instead of throwing, forks of a running sandbox with its memory, network allow lists set on the host, secrets the sandbox never sees, and idlePauseSeconds. The calls map one to one (migration):

TypeScriptimport { Sandbox } from "withruntime";const box = await Sandbox.create({ funding: "trial" });try {  console.log((await box.exec("python3 -c 'print(6 * 7)'", { check: true })).stdout);} finally {  await box.stop();}

Mistakes and how Runtime handles them

• An SDK older than 0.4.0. The withruntime/e2b entry point arrived in 0.4.0. Upgrade the package.
• Keeping only the E2B key. Runtime needs its own: set RUNTIME_API_KEY, or rely on the machine's saved connection.
• Relying on sandboxes that pause forever. A paused Runtime sandbox is kept for the retention you set, up to 365 days on a paid account, 30 by default.
• Forgetting the switching credit. Before your first top-up, run npx withruntime switch --from e2b; that top-up is matched with credit, up to $100.

Then check the saving on your own runs with runtime compare --from e2b (how to compare your costs).

Related

• E2B alternatives and E2B vs Daytona
• E2B pricing calculator
• JavaScript SDK and Python SDK

Sources

• E2B pricing, checked 23 September 2026

Facts on this page were checked on 25 September 2026.