COMPARISON GUIDE

Free Code Execution API Comparison 2026

Compare online code execution APIs side-by-side. Run code in 40-80+ languages via a simple HTTP request. Support for competitive programming, AI agents, and coding interviews.

Last updated: March 2026 | 6 providers compared

What Do Developers Use Code Execution APIs For?

Code execution APIs replace self-hosted runtime environments with a single HTTP call. Here are the most common use cases:

💈
Coding interviews & LeetCode
🏆
Competitive programming
🏫
AI code agent execution
💾
Online IDE + code editor
🤖
Code assessment platform
🗸
Educational tool + sandbox

Quick Comparison

Feature matrix across all 6 code execution APIs. Scroll horizontally on mobile.

Provider Free Tier Languages Timeout stdin/stdout Session State Pricing
Judge0 2,000/day Free 60+ 2-15s Yes Stateless €27/mo
OneCompiler 10,000/mo Free 70+ 7-20s Yes Stateless $5/mo
Sphere Engine Contact Trial 80+ 5-10s Yes Stateless Custom
Piston No free Paid only 50+ 10-30s Yes Stateless Contact
E2B $100 credit Free Any 24h sessions Yes Stateful $0.05/hr
Frostbyte Best Value 200 credits Free 4 (Python, JS, TS, Bash) 30s Yes Stateless $1 = 500

Provider Breakdown

Detailed pros/cons for each code execution API. Click provider names for their documentation.

Judge0

Most balanced, 60+ languages
2,000 free/day €27/mo starter 60+ languages
  • 60+ languages out-of-box
  • stdin/stdout support
  • Webhooks for async
  • Open-source (self-host)
  • RapidAPI integration
  • 2,000 submissions/day limit
  • Stateless (no session)
  • €27/mo minimum paid
  • No real-time output

OneCompiler

Most languages, coding challenges
10,000 free/mo $5/mo starter 70+ languages
  • 70+ programming languages
  • Embedded editor widget
  • Challenge APIs for contests
  • Web scraping built-in
  • Studio IDE integration
  • No free tier for Studio
  • Limited timeout (7s free)
  • No file upload
  • Single-execution model

Sphere Engine

Enterprise, 80+ languages
80+ languages RESTful API Web widgets
  • Widest language support
  • Multiple APIs (Compilers, Problems, Containers)
  • Web widget integration
  • Detailed execution results
  • Enterprise-grade SLA
  • No free tier (custom pricing)
  • Complex setup for developers
  • Limited documentation for startups
  • Requires business inquiry

Piston

Self-hosted, open-source (paid now)
50+ languages Open source No free API
  • Open-source (engineer-man/piston)
  • Self-host on own infrastructure
  • Full language customization
  • No vendor lock-in
  • Public API no longer free (Feb 2026)
  • Must self-host for free access
  • Requires Docker + infrastructure
  • Limited client libraries

E2B

Best for AI agents, 24h sessions
$100 free credit 24h sessions Stateful VMs
  • Stateful sandboxes (full VM)
  • 24-hour session duration
  • Real filesystem access
  • Firecracker microVMs
  • AI agent optimization
  • BYOC/on-prem options
  • No free tier (but $100 credit)
  • More expensive than stateless
  • Overkill for simple code runs
  • Slower startup (~80ms)

Frostbyte Best Value

Simplest API, 200 free credits
200 free credits $0.002/execution 40+ APIs total
  • No signup form (1 API call)
  • 200 free credits, no CC
  • Python, JavaScript, TypeScript, Bash
  • stdin/stdout support
  • Pay-as-you-go ($1 = 500)
  • 40+ other APIs included
  • Only 4 languages
  • No session state
  • No file uploads
  • Simplicity trade-off

Code Examples

How to execute code with each API. Click tabs to see different languages.

Judge0 Example

cURL
JavaScript
Python
# 1. Submit code for execution
curl -X POST https://judge0-ce.p.rapidapi.com/submissions \
  -H 'Content-Type: application/json' \
  -H 'X-RapidAPI-Key: YOUR_KEY' \
  -H 'X-RapidAPI-Host: judge0-ce.p.rapidapi.com' \
  -d '{
    "language_id": 71,
    "source_code": "print(\"Hello, World!\")",
    "stdin": "test input"
  }'

# Returns token, e.g. "token": "abc123def456"

# 2. Get execution result
curl https://judge0-ce.p.rapidapi.com/submissions/abc123def456 \
  -H 'X-RapidAPI-Key: YOUR_KEY' \
  -H 'X-RapidAPI-Host: judge0-ce.p.rapidapi.com'
const fetch = await import('node-fetch');

const code = `
print("Hello, World!")
print(input())
`;

// Submit code
const submitRes = await fetch.default(
  'https://judge0-ce.p.rapidapi.com/submissions',
  {
    method: 'POST',
    headers: {
      'Content-Type': 'application/json',
      'X-RapidAPI-Key': process.env.RAPIDAPI_KEY
    },
    body: JSON.stringify({
      language_id: 71, // Python
      source_code: code,
      stdin: 'test'
    })
  }
);

const { token } = await submitRes.json();

// Poll for result
const resultRes = await fetch.default(
  `https://judge0-ce.p.rapidapi.com/submissions/${token}`,
  { headers: { 'X-RapidAPI-Key': process.env.RAPIDAPI_KEY } }
);
const result = await resultRes.json();

console.log('stdout:', result.stdout);
console.log('stderr:', result.stderr);
import requests
import time

code = """
print("Hello, World!")
print(input())
"""

headers = {
    'X-RapidAPI-Key': 'YOUR_KEY',
    'Content-Type': 'application/json'
}

# Submit
resp = requests.post(
    'https://judge0-ce.p.rapidapi.com/submissions',
    headers=headers,
    json={'language_id': 71, 'source_code': code, 'stdin': 'test'}
)
token = resp.json()['token']

# Poll result
for _ in range(10):
    result = requests.get(
        f'https://judge0-ce.p.rapidapi.com/submissions/{token}',
        headers=headers
    ).json()
    if result['status']['id'] > 2:
        print(result['stdout'])
        break
    time.sleep(0.5)

OneCompiler Example

cURL
JavaScript
# OneCompiler API - Execute code
curl -X POST https://api.onecompiler.com/api/v1/code/exec \
  -H 'Content-Type: application/json' \
  -H 'Authorization: Bearer YOUR_API_KEY' \
  -d '{
    "language": "python",
    "code": "print(\"Hello, World!\")",
    "stdin": ""
  }'
const apiKey = process.env.ONECOMPILER_API_KEY;

const response = await fetch(
  'https://api.onecompiler.com/api/v1/code/exec',
  {
    method: 'POST',
    headers: {
      'Content-Type': 'application/json',
      'Authorization': `Bearer ${apiKey}`
    },
    body: JSON.stringify({
      language: 'python',
      code: 'print("Hello from OneCompiler")',
      stdin: ''
    })
  }
);

const result = await response.json();
console.log(result.stdout);
console.log(result.stderr);

Frostbyte Code Runner Example

cURL
JavaScript
# No API key needed for basic use
curl -X POST https://agent-gateway-kappa.vercel.app/v1/agent-coderunner/api/execute \
  -H 'Content-Type: application/json' \
  -d '{
    "language": "python",
    "code": "print(42 + 58)"
  }'

# With API key (for higher limits)
curl -X POST https://agent-gateway-kappa.vercel.app/api/keys/create
# Then add: -H 'Authorization: Bearer YOUR_KEY'
// Execute code (no API key needed for basic use)
const result = await fetch(
  'https://agent-gateway-kappa.vercel.app/v1/agent-coderunner/api/execute',
  {
    method: 'POST',
    headers: { 'Content-Type': 'application/json' },
    body: JSON.stringify({
      language: 'python',
      code: 'import sys\nprint(f"Python {sys.version}")\nprint(42 + 58)'
    })
  }
).then(r => r.json());

console.log(result.stdout);   // "Python 3.12.x\n100"
console.log(result.exitCode); // 0
console.log(result.duration);  // ~12ms

Pricing Comparison

What you pay at each tier. Free options are limited; consider paid plans for production use.

Judge0
€27/mo
2,000/day submissions
Free: 2K/day
OneCompiler
$5/mo
10,000/month
Free: 10K/mo
Sphere Engine
Custom
Enterprise pricing
Trial available
Piston
Contact
No free API tier
Self-host: free
E2B
$0.05/hour
$100 free credit
Free: 1vCPU sandbox
Frostbyte
$1 one-time
500 executions
Free: 200 credits

Cost Comparison at Scale (1,000 executions)

Provider 1K executions 10K executions 100K executions
Judge0€27/mo (2K/day included)€27/mo€27/mo
OneCompiler$5/mo$5/mo$25/mo (100K)
Sphere EngineContactContactContact
PistonContactContactContact
E2B~$1.25 (25 min)~$12.50~$125
Frostbyte$2$20$200

Which Code Execution API Should You Use?

Choose based on your specific requirements:

💈 Coding Interviews/LeetCode

Use Judge0 or OneCompiler. Both support 60-70+ languages, stdin/stdout, and have low-latency APIs optimized for rapid-fire code submissions. OneCompiler cheaper at $5/mo, Judge0 more language-rich.

🏫 AI Code Agent

Use E2B for stateful sandboxes with file system access (perfect for Claude Code, autonomous agents). Use Frostbyte if you just need simple Python/JavaScript execution in pipelines.

🏆 Competitive Programming

Use OneCompiler (70+ languages, challenges API) or Judge0 (60+ languages, webhooks for async results). Both scale well for high-volume submissions.

🤖 Online IDE / Code Editor

Use OneCompiler (embedded editor widget, web interface) or Sphere Engine (enterprise solution with web components). Judge0 is API-only.

💾 Educational Platform

Use OneCompiler or Sphere Engine for assessment features (auto-grading, problem sets, student tracking). Both have tools/APIs for building classroom platforms.

🗸 Simplest Setup

Use Frostbyte (no signup form, one API call to get key). Next best: Judge0 or OneCompiler on RapidAPI.

Try It Live

Execute code right now using the Frostbyte Code Runner API. No signup required.

Try Frostbyte Code Runner for Free

200 free credits. No signup form, no credit card. Execute Python, JavaScript, TypeScript, or Bash code with a single API call.

Get Free API Key See Code Example

Frequently Asked Questions

What is a code execution API?
A code execution API lets you submit code (as a string) to a remote server and get back the output (stdout), errors (stderr), and exit status. Instead of managing your own runtime, sandboxing, and timeout logic, you send an HTTP request with the code and get results. This is essential for online judges, coding interview platforms, and AI agents.
What is the best free code execution API?
Judge0 offers 2,000 submissions/day free with 60+ languages. OneCompiler offers 10,000/month free with 70+ languages. E2B offers $100 free credit (good for AI agents). Frostbyte offers 200 free credits for Python/JS/TS/Bash. Best choice depends on your use case: volume, languages, and stateful vs. stateless execution.
Can I run code with custom input (stdin)?
Yes. Judge0, OneCompiler, Sphere Engine, Piston, and Frostbyte all support stdin. You pass your input as part of the API request (either as a field or in the request body), and the code reads from stdin using language-specific functions (input() in Python, readline in JavaScript, etc.).
What's the difference between stateful and stateless execution?
Stateless (Judge0, OneCompiler, Frostbyte) runs each code submission in isolation. Each execution is independent — no shared files, no memory between runs. Stateful (E2B) keeps a long-lived sandbox session where you can create files, install packages, and run multiple commands with shared context. Stateful is better for AI agents, stateless is cheaper for simple one-off runs.
What languages does each API support?
Judge0: 60+ (Python, Java, C++, JavaScript, Go, Ruby, Rust, etc.). OneCompiler: 70+ (adds more web languages). Sphere Engine: 80+ (most comprehensive). Piston: 50+. E2B: Any (bring Docker image). Frostbyte: 4 (Python, JavaScript, TypeScript, Bash).
What timeout limits apply to code?
Judge0: 2-15 seconds (depends on plan). OneCompiler: 7-20 seconds. Sphere Engine: 5-10 seconds. Piston: 10-30 seconds. Frostbyte: 30 seconds. E2B: 24-hour sessions (for agents). Most free tiers have short timeouts to prevent abuse.
Can I use code execution APIs in serverless functions?
Yes. All of these APIs are HTTP-based, so they work in AWS Lambda, Google Cloud Functions, Vercel, and any other serverless platform. You don't need to bundle a runtime; just make an HTTP request to the API. This is much simpler than trying to run Piston or Judge0 self-hosted in a Lambda.