[Blog](https://scrapfly.io/blog) / [http](https://scrapfly.io/blog/tag/http) / [What is HTTP 401 Error and How to Fix it](https://scrapfly.io/blog/posts/what-is-http-401-error-and-how-to-fix-it) # What is HTTP 401 Error and How to Fix it by [Ziad Shamndy](https://scrapfly.io/blog/author/ziad) Mar 24, 2026 10 min read [\#http](https://scrapfly.io/blog/tag/http) [ ](https://www.linkedin.com/sharing/share-offsite/?url=https%3A%2F%2Fscrapfly.io%2Fblog%2Fposts%2Fwhat-is-http-401-error-and-how-to-fix-it "Share on LinkedIn") Have you ever been stopped in your tracks by a "401 error" while trying to access a website, application, or API? This seemingly cryptic message, often accompanied by the term “401 Unauthorized” or “HTTP 401 error”. It’s a common yet frustrating issue that signals a problem with your credentials or authorization. In this guide, we'll break down the HTTP status 401 in simple terms, explore its root causes, make a small Flask server to simulate it and explore some tips on how to avoid it by correctly authenticating your requests. ## Key Takeaways Fix HTTP 401 "Unauthorized" errors by providing correct authentication credentials, checking token expiration, and ensuring proper header formatting to successfully access protected web resources and APIs. - HTTP 401 "Unauthorized" occurs when server refuses to authorize a request due to failed authentication - Authentication failure is the root cause - missing, incorrect, or expired credentials prevent access to protected resources - Multiple authentication methods exist - Basic Auth, JWT tokens, API keys, and session-based authentication each have different requirements - WWW-Authenticate header specifies requirements - server indicates which authentication method is needed (Basic, Bearer, etc.) - Client-side fixes involve credential management - verify username/password, check token expiration, ensure proper header formatting - Server-side solutions require proper configuration - implement authentication mechanisms, validate credentials, and provide clear error messages - Web scraping implications - HTTP 401 is common when accessing protected APIs or websites that require authentication - Debugging requires systematic approach - check headers, tokens, server responses, and authentication flow to identify the specific issue **Get web scraping tips in your inbox**Trusted by 100K+ developers and 30K+ enterprises. Unsubscribe anytime. ## What is HTTP 401 Error? The HTTP 401 Unauthorized error is a status code 401 returned by the server when authentication fails. It means the server has received your request, but it refuses to authorize it. ### **What Does a 401 Error Response Look Like?** Here is an example of a typical **401 HTTP code** response: http```http HTTP/1.1 401 Unauthorized Content-Type: text/html WWW-Authenticate: Basic realm="Access to the site" ``` - **HTTP/1.1 401 Unauthorized**: The status code indicating failed authentication. - **WWW-Authenticate**: This header specifies the type of authentication required (e.g., “Basic” authentication). ### Other Names for 401 Unauthorized The HTTP 401 error can appear in slightly different forms depending on the system or tool you are using. Here are some alternative names for this error: - **401 Unauthorized** - **HTTP 401 error** - **Error code 401** - **HTTP status code 401** - **401 status code** Regardless of how it is displayed, all these terms point to the same issue: the server needs valid credentials to fulfill your request. ## HTTP 401 Server Example Here’s a basic implementation in **Flask** to show how an HTTP server checks for authentication and returns a **401 error**: python```python from flask import Flask, request, jsonify app = Flask(__name__) @app.route('/secure-endpoint') def secure_endpoint(): auth = request.headers.get('Authorization') if not auth or auth != "Bearer ValidToken": return jsonify({"error": "Unauthorized"}), 401 return jsonify({"message": "Welcome to the secure endpoint!"}) if __name__ == '__main__': app.run() ``` 1. **Authentication Check**: - The server retrieves the `Authorization` header from the incoming request. - If the header is missing or doesn’t match the expected value (e.g., `Bearer ValidToken`), the server returns a **401 status code**. 2. **Unauthorized Response**: - The response body contains an error message like this:json```json { "error": "Unauthorized" } ``` - The **401 HTTP code** indicates that the server recognizes the request but refuses to authorize it due to invalid credentials. 3. **Valid Access**: - If the `Authorization` header contains the correct credentials (`Bearer ValidToken`), the server returns a success message:json```json { "message": "Welcome to the secure endpoint!" } ``` Using this small Flask web application you can easily test how your clients handle the 401 error code. ## Common HTTP Authentication Methods Different systems use various authentication mechanisms to protect resources and validate users or clients. However, errors in implementation, expired credentials, or incorrect requests can lead to an **HTTP 401 error**. Below is a detailed overview of the most common authentication methods, pitfalls that can trigger a **401 Unauthorized error**, and practical debugging tips. ### 1. Basic Authentication Basic Authentication uses the **`Authorization` header**, where the `username:password` combination is base64-encoded. It’s a simple yet widely used method for HTTP requests. **Example:** http```http Authorization: Basic dXNlcjpwYXNzd29yZA== ``` **How to Check:** - Inspect the `Authorization` header in the request. - Review the response headers for hints such as `WWW-Authenticate: Basic realm="Your Realm"`. **Tips**: - Ensure the credentials are correctly base64-encoded. - Your client might have different base64 encoding methods: use the standard base64 encode **not the URL-safe base64 encoding**. ### 2. Token-Based Authentication Token-based authentication requires a secure token (e.g., JWT, OAuth tokens) to be sent in the request headers. Typically, the format looks like: http```http Authorization: Bearer ``` **How to Check:** - Log or print the token being sent. - Review the server response headers for clues such as `WWW-Authenticate: Bearer`. **Tips**: - Verify the token is not expired or revoked in the web dashboard where it was generated. - Ensure the token is correctly formatted and sent in the `Authorization` header. ### 3. API Key Authentication An API key is provided either in the headers, query parameters, or body to authenticate a client. Example: http```http Authorization: Api-Key YOUR_API_KEY ``` **How to Check:** - Review the outgoing request headers and query parameters. - Log the API key and compare it to the one expected by the server. **Tips**: - Verify that the API key is still valid by checking the API provider’s dashboard. Often API keys are rotated or revoked. - Ensure the API key is correctly placed in the request headers or query parameters. ### 4. Session-Based Authentication Session-based authentication uses cookies to track user sessions after login. The client stores a session ID and sends it with each request to maintain access. **How to Check:** - Use browser tools (like DevTools) to verify cookies are sent in requests. - Look at server logs to confirm if the session ID is expired or invalid. **Tips**: - Check the session timeout settings on server or dashboard if available. - Often timeout is very low for security reasons and not reported anywhere so it's best to start a fresh session for each action. ### 5. Digest Authentication Digest Authentication is a more secure alternative to Basic Auth. It uses hashing algorithms to send credentials securely. The `Authorization` header includes hashed credentials. **Example Header:** http```http Authorization: Digest username="user", realm="example", nonce="random", uri="/path", response="hashed_value" ``` **How to Check:** - Inspect the `Authorization` header for accuracy. - Review the server response for a `401` status with a `WWW-Authenticate: Digest` challenge. **Tips**: - Review how the hash is computed and ensure it matches the server’s expectations. ### 6. JWT Authentication JSON Web Tokens (JWT) are commonly used for secure API authentication. They are sent in the `Authorization` header with the format: http```http Authorization: Bearer ``` **How to Check:** - Decode the token and inspect its payload. - Verify the expiration (`exp`) and issued-at (`iat`) times. - Confirm the token matches the expected format (Header.Payload.Signature). **Tips**: - Use a JWT debugger to decode and verify the token. Never expose the token to untrusted parties like web JWT debuggers. - Check the token’s expiration and issued-at times to ensure it’s still valid. --- ### **Summary Table of Authentication Methods** | **Authentication Method** | **Common Pitfalls** | **Debugging Tips** | |---|---|---| | **Basic Authentication** | Missing/invalid credentials | Verify header format and base64 encode. | | **Token-Based Auth** | Expired or malformed token | Check token validity and format. | | **API Key Authentication** | Missing or invalid API key | Validate API key placement and value. | | **Session-Based Auth** | Expired session or missing cookies | Verify cookies and session timeout. | | **Digest Authentication** | Invalid hash or outdated nonce | Recompute hash and check `WWW-Authenticate`. | | **JWT Authentication** | Expired or malformed JWT | Decode JWT and verify claims. | By understanding these **common authentication methods**, their pitfalls, and debugging strategies, you can quickly identify why a **401 Unauthorized error** occurs and resolve it effectively. Scrapfly #### Scale your web scraping effortlessly Scrapfly handles proxies, browsers, and anti-bot bypass — so you can focus on data. [Try Free →](https://scrapfly.io/register)## 401 vs 403: What’s the Difference? The **401 Unauthorized** and **403 Forbidden** errors are both HTTP status codes that indicate access issues, but they have distinct meanings and causes. ### What is a 401 Error? The request lacks valid authentication credentials. The server cannot verify who you are because the credentials are missing, invalid, or expired. **Example Response for a 401 Error:** http```http HTTP/1.1 401 Unauthorized Content-Type: application/json WWW-Authenticate: Bearer realm="Access to the resource" { "error": "Unauthorized", "message": "Invalid credentials provided." } ``` **When You See This Error:** You need to provide valid credentials, fix formatting issues in the `Authorization` header, or ensure the token is still valid. The server expects authentication, but you haven’t provided it correctly. ### **What is a 403 Error?** The server recognizes who you are (authentication is successful), but you do not have the necessary permissions to access the requested resource. **Example Response for a 403 Error:** http```http HTTP/1.1 403 Forbidden Content-Type: application/json { "error": "Forbidden", "message": "You do not have permission to access this resource." } ``` **When You See This Error:** You are authenticated, but the server has denied access to the resource based on permissions or rules. This often requires an adjustment of user roles or permissions. ## published\_at: 2022-01-01 ### **Key Differences Between 401 and 403** | **Aspect** | **401 Unauthorized** | **403 Forbidden** | |---|---|---| | **Definition** | Authentication failed or credentials missing. | Authentication successful, but access denied. | | **When It Happens** | The server cannot identify the user. | The server recognizes the user but restricts access. | | **Common Causes** | Missing or invalid credentials, expired tokens or sessions, missing `Authorization` header. | Insufficient permissions, resource-specific restrictions, IP or location blocking, rule-based access denial. | | **How to Resolve** | Provide valid credentials, refresh expired tokens or sessions, ensure the `Authorization` header is correct. | Verify and update user permissions, adjust access control rules, contact the administrator for access. | Understanding the difference between these two errors can help you diagnose and resolve access problems more effectively. ## Power-Up with Scrapfly ScrapFly provides [web scraping](https://scrapfly.io/docs/scrape-api/getting-started), [screenshot](https://scrapfly.io/docs/screenshot-api/getting-started), and [extraction](https://scrapfly.io/docs/extraction-api/getting-started) APIs for data collection at scale. - [Anti-bot protection bypass](https://scrapfly.io/docs/scrape-api/anti-scraping-protection) - scrape web pages without blocking! - [Rotating residential proxies](https://scrapfly.io/docs/scrape-api/proxy) - prevent IP address and geographic blocks. - [JavaScript rendering](https://scrapfly.io/docs/scrape-api/javascript-rendering) - scrape dynamic web pages through cloud browsers. - [Full browser automation](https://scrapfly.io/docs/scrape-api/javascript-scenario) - control browsers to scroll, input and click on objects. - [Format conversion](https://scrapfly.io/docs/scrape-api/getting-started#api_param_format) - scrape as HTML, JSON, Text, or Markdown. - [Full screenshot customization](https://scrapfly.io/docs/screenshot-api/getting-started#api_param_capture) - scroll and capture exact areas. - [Comprehensive options](https://scrapfly.io/docs/screenshot-api/getting-started) - block banners, use dark mode, and more. - [LLM prompts](https://scrapfly.io/docs/extraction-api/llm-prompt) - extract data or ask questions using LLMs - [Extraction models](https://scrapfly.io/docs/extraction-api/automatic-ai) - automatically find objects like products, articles, jobs, and more. - [Extraction templates](https://scrapfly.io/docs/extraction-api/rules-and-template) - extract data using your own specification. - [Python](https://scrapfly.io/docs/sdk/python) and [Typescript](https://scrapfly.io/docs/sdk/typescript) SDKs, as well as [Scrapy](https://scrapfly.io/docs/sdk/scrapy) and [no-code tool integrations](https://scrapfly.io/docs/integration/getting-started). ## FAQ Can IP restrictions cause a 401 error?Typically, IP restrictions result in a 403 Forbidden error. A 401 error specifically relates to failed or missing authentication, not IP-based access denial. What is the difference between 401 Unauthorized and 403 Forbidden?401 Unauthorized: Authentication has failed, or no credentials were provided (server does not know who you are). 403 Forbidden: Authentication succeeded, but you lack permission to access the resource (server knows who you are but blocks access). How to fix "Request failed with status code 401"?1. Verify your credentials (username, password, token, API key). 2. Check the server logs or API response for more details. 3. Ensure your token or session has not expired. ## Summary We explored the HTTP 401 error meaning, common causes, and solutions. The 401 status code signals authentication failure, which can arise due to various authentication methods such as Basic Auth, JWT, API keys, or sessions. Understanding how HTTP 401 unauthorized errors occur and knowing how to debug them can save valuable time when troubleshooting access issues. Always check headers, tokens, and server responses for the best debugging results. By mastering HTTP status code 401, you'll be better equipped to resolve these errors in the future. Table of Contents- [Key Takeaways](#key-takeaways) - [What is HTTP 401 Error?](#what-is-http-401-error) - [What Does a 401 Error Response Look Like?](#what-does-a-401-error-response-look-like) - [Other Names for 401 Unauthorized](#other-names-for-401-unauthorized) - [HTTP 401 Server Example](#http-401-server-example) - [Common HTTP Authentication Methods](#common-http-authentication-methods) - [1. Basic Authentication](#1-basic-authentication) - [2. Token-Based Authentication](#2-token-based-authentication) - [3. API Key Authentication](#3-api-key-authentication) - [4. Session-Based Authentication](#4-session-based-authentication) - [5. Digest Authentication](#5-digest-authentication) - [6. JWT Authentication](#6-jwt-authentication) - [Summary Table of Authentication Methods](#summary-table-of-authentication-methods) - [401 vs 403: What’s the Difference?](#401-vs-403-what-s-the-difference) - [What is a 401 Error?](#what-is-a-401-error) - [What is a 403 Error?](#what-is-a-403-error) - [published\_at: 2022-01-01](#published-at-2022-01-01) - [Key Differences Between 401 and 403](#key-differences-between-401-and-403) - [Power-Up with Scrapfly](#power-up-with-scrapfly) - [FAQ](#faq) - [Summary](#summary) Join the Newsletter Get monthly web scraping insights Scale Your Web Scraping Anti-bot bypass, browser rendering, and rotating proxies, all in one API. Start with 1,000 free credits. No credit card required 1,000 free API credits Anti-bot bypass included [Start Free](https://scrapfly.io/register) [View Docs](https://scrapfly.io/docs/onboarding) Not ready? Get our newsletter instead. ## Explore this Article with AI [ ChatGPT ](https://chat.openai.com/?q=Summarize%20this%20page%3A%20https%3A%2F%2Fscrapfly.io%2Fblog%2Fposts%2Fwhat-is-http-401-error-and-how-to-fix-it) [ Gemini ](https://www.google.com/search?udm=50&aep=11&q=Summarize%20this%20page%3A%20https%3A%2F%2Fscrapfly.io%2Fblog%2Fposts%2Fwhat-is-http-401-error-and-how-to-fix-it) [ Grok ](https://x.com/i/grok?text=Summarize%20this%20page%3A%20https%3A%2F%2Fscrapfly.io%2Fblog%2Fposts%2Fwhat-is-http-401-error-and-how-to-fix-it) [ Perplexity ](https://www.perplexity.ai/search/new?q=Summarize%20this%20page%3A%20https%3A%2F%2Fscrapfly.io%2Fblog%2Fposts%2Fwhat-is-http-401-error-and-how-to-fix-it) [ Claude ](https://claude.ai/new?q=Summarize%20this%20page%3A%20https%3A%2F%2Fscrapfly.io%2Fblog%2Fposts%2Fwhat-is-http-401-error-and-how-to-fix-it) ## Related Articles [ http python ### How to Fix 403 Forbidden Errors When Web Scraping Learn why web scrapers get 403 Forbidden errors and how to fix them with 7 Python solutions, from headers to TLS fingerp... ](https://scrapfly.io/blog/posts/403-forbidden-web-scraping) [ http api ### What HTTP Error 412 Precondition Failed and How to Fix it? Quick look at HTTP status code 412 - what does it mean, its common causes, and how it can be prevented. ](https://scrapfly.io/blog/posts/what-is-http-412-error-precondition-failed) [ http ### What is HTTP 422 Error? (Unprocessable Entity) 422 Unprocessable Entity error is usually caused by a semantically invalid request. Learn http error 422 causes and how ... ](https://scrapfly.io/blog/posts/what-is-http-422-error-unprocessable-entity) ## Related Questions - [ Q What are Cloudflare Errors 1006, 1007, 1008? ](https://scrapfly.io/blog/answers/cloudflare-error-1006-1007-1008-access-denied) - [ Q How to add headers to every or some scrapy requests? ](https://scrapfly.io/blog/answers/how-to-add-headers-to-every-or-some-scrapy-requests) Scale your web scraping effortlessly, **1,000 free credits** [Start Free](https://scrapfly.io/register)