Reference

Error Codes Reference

Complete reference for AlterLab API errors, status codes, and how to handle them gracefully.

Error Response Structure

All errors return a consistent JSON structure with error,message, and optional details fields. Check the HTTP status code first, then parse the response body for details.

HTTP Status Codes

Code	Status	Description	Retry?
200	OK	Request succeeded (sync response with content)	N/A
202	Accepted	Job queued for async processing (poll job_id)	N/A
204	No Content	Successful deletion, no response body	N/A
400	Bad Request	Invalid request parameters or malformed JSON	No
401	Unauthorized	Missing, invalid, or expired API key/token	No
402	Payment Required	Insufficient balance or paywall detected	No
403	Forbidden	Access denied by target site or blocked by anti-bot	Maybe
404	Not Found	Resource not found (job, webhook, etc.)	No
409	Conflict	Duplicate resource (webhook URL already exists)	No
413	Payload Too Large	Content exceeds size limit (10MB)	No
415	Unsupported Media	URL content type not supported for requested mode	No
422	Unprocessable	All scraping tiers failed or content extraction failed	Maybe
429	Too Many Requests	Rate limit exceeded, check Retry-After header	Yes (after delay)
500	Internal Error	Unexpected server error	Yes
502	Bad Gateway	Upstream error or worker queue issue	Yes
503	Service Unavailable	Service temporarily unavailable or target site down	Yes
504	Gateway Timeout	Request timed out waiting for response	Yes

Scraping Errors

These errors occur during the scraping process. Most result in automatic refunds.

BLOCKED_BY_ANTIBOT

403

Refunded

The target site detected and blocked the scraping attempt. All tier escalations failed.

Solution: Try using max_tier: "4" to enable CAPTCHA solving, or contact support for sites with advanced protection.

CHALLENGE_DETECTED

403

Refunded

A bot detection challenge (anti-bot wall, reCAPTCHA, hCaptcha) was encountered.

Solution: Enable JavaScript rendering with mode: "js" or increase max tier.

TIMEOUT

504

Refunded

The scraping operation timed out before completing.

Solution: Increase timeout parameter or use async mode with polling.

CONTENT_TOO_LARGE

413

Refunded

The page content exceeds the 10MB size limit.

Solution: Target a specific section of the page or use a different scraping strategy.

UNSUPPORTED_CONTENT_TYPE

415

Refunded

The URL returns a content type not supported by the selected mode.

Solution: Use the appropriate mode - pdf for PDFs, ocr for images.

EXTRACTION_FAILED

422

Refunded

Content was fetched but could not be parsed or extracted.

Solution: Check if the URL returns valid HTML/content. Try a different extraction mode.

REQUIRES_AUTH

401

Refunded

The page requires authentication to access.

Solution: This URL is behind a login wall and cannot be scraped without credentials.

PAYWALL_DETECTED

402

Refunded

The content is behind a paywall and requires subscription to access.

Solution: Content requires paid subscription. Cannot be accessed via scraping.

NETWORK_ERROR

503

Refunded

Network connection failed - DNS error, connection refused, or SSL error.

Solution: Verify the URL is valid and the site is online. Retry after a brief delay.

Authentication Errors

INVALID_API_KEY

401

The API key provided is invalid, malformed, or has been revoked.

Solution: Check that your API key starts with sk_live_ or sk_test_ and is active in your dashboard.

MISSING_API_KEY

401

No API key was provided in the request headers.

Solution: Include the X-API-Key header with your API key.

SESSION_EXPIRED

401

The session token (for dashboard APIs) has expired.

Solution: Log in again to get a fresh session token.

Session Errors (Authenticated Scraping)

Errors related to authenticated scraping (BYOS) session management and usage.

SESSION_NOT_FOUND

404

The provided session_id does not exist or belongs to another user.

Solution: Verify the UUID. Use GET /sessions to list your valid sessions.

SESSION_EXPIRED

410

The session cookies have expired or the session was marked as expired after repeated validation failures.

Solution: Log in to the target site again and call POST /sessions/:id/refresh with fresh cookies.

SESSION_DOMAIN_MISMATCH

400

The scrape URL domain does not match the session's stored domain. For example, using an amazon.com session to scrape walmart.com.

Solution: Create a separate session for each target domain.

SESSION_INACTIVE

410

The session has been deleted or disabled.

Solution: Create a new session with fresh cookies.

SESSION_LIMIT_REACHED

429

Maximum number of sessions per account (50) has been reached.

Solution: Delete unused or expired sessions. Use GET /sessions?status=expired to find candidates for cleanup.

SESSION_COOKIES_CONFLICT

400

Both session_id and cookies were provided in the scrape request. These parameters are mutually exclusive.

Solution: Use either session_id (for stored sessions) or cookies (for inline one-off use), not both.

Billing Errors

INSUFFICIENT_CREDITS

402

Your account has insufficient balance to complete this request.

Solution: Check your balance with GET /api/v1/usage and upgrade your plan or add funds.

EXCEEDS_COST_LIMIT

400

The estimated cost exceeds your max_credits limit.

Solution: Increase max_credits or use a simpler scraping mode.

SUBSCRIPTION_INACTIVE

402

Your subscription has been cancelled or payment failed.

Solution: Check your billing status in the dashboard and update payment method if needed.

Rate Limit Errors

RATE_LIMIT_EXCEEDED

429

You have exceeded your plan's rate limit (requests per minute).

Solution: Check the X-RateLimit-Reset header for when to retry.

Rate Limit Headers:

X-RateLimit-Limit: Your plan's rate limit
X-RateLimit-Remaining: Requests remaining in window
X-RateLimit-Reset: Unix timestamp when limit resets

Plan	Rate Limit	Burst Limit
Free	30 req/min	5 req/sec
Basic	60 req/min	10 req/sec
Growth	100 req/min	20 req/sec
Scale	300 req/min	30 req/sec
High Volume	500 req/min	50 req/sec

Refund Policy

Costs are automatically refunded for most error conditions where the scraping failed through no fault of the user.

Costs Refunded

Site blocked access (403, anti-bot)
Request timeout
Network/connection errors
Content extraction failed
Unsupported content type
Page requires authentication
Paywall detected
Server errors (5xx)

Costs NOT Refunded

Successful scrape (any tier)
Cache hit (free)
Invalid API key
Rate limit exceeded
Invalid request parameters
Cancelled by user

Refund Timing

Refunds are processed instantly when an error occurs. Check the billing.refundedfield in error responses to confirm.

Error Response Format

JSON

{"error":"INSUFFICIENT_CREDITS","message":"Your account has insufficient balance for this request","request_id":"req_550e8400-e29b-41d4-a716-446655440000","details":{"required_credits":5,"available_credits":2,"estimated_tier":"2"}}

Field	Type	Description
error	string	Machine-readable error code
message	string	Human-readable error description
request_id	string?	Unique request ID for support inquiries
details	object?	Additional context about the error

Handling Errors

Python

import time
import requests
from requests.exceptions import RequestException

defscrape_with_error_handling(url:str, api_key:str, max_retries:int=3):"""Scrape with proper error handling and retries."""
for attempt inrange(max_retries):try: response = requests.post("https://api.alterlab.io/api/v1/scrape", headers={"X-API-Key": api_key}, json={"url": url}, timeout=60)
# Successif response.status_code in(200,202):return response.json()
# Parse error response error = response.json() error_code = error.get("error","UNKNOWN")
# Don't retry client errorsif response.status_code in(400,401,402,404,409,415):raise Exception(f"Client error: {error_code} - {error.get('message')}")
# Rate limited - wait and retryif response.status_code ==429: reset_time =int(response.headers.get("X-RateLimit-Reset",0)) wait_time =max(reset_time - time.time(),60)print(f"Rate limited. Waiting {wait_time}s...") time.sleep(wait_time)continue
# Server error - retry with backoffif response.status_code >=500: wait_time =2** attempt
print(f"Server error {response.status_code}. Retrying in {wait_time}s...") time.sleep(wait_time)continue
# 422 - All tiers failed, might want to try different settingsif response.status_code ==422:raise Exception(f"Scraping failed: {error.get('message')}")
except RequestException as e:if attempt < max_retries -1: time.sleep(2** attempt)continueraise
raise Exception(f"Max retries ({max_retries}) exceeded")

Rate Limits Changelog

Last updated: June 2026

URL: https://alterlab.io/docs/reference/error-codes

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Error Codes Reference

HTTP Status Codes

Scraping Errors

Authentication Errors

Session Errors (Authenticated Scraping)

Billing Errors

Rate Limit Errors

Refund Policy

Costs Refunded

Costs NOT Refunded

Error Response Format

Handling Errors