Why Redirect and rewrite rules in Firebase? - Purpose & Use Cases

The Big Idea

What if you could fix broken links instantly without changing a single line of your website code?

The Scenario

Imagine you have a website and you want to change some page addresses or send visitors to new pages without breaking links.

You try to do this by manually changing every link in your code and telling your team to update bookmarks.

The Problem

This manual way is slow and confusing.

It’s easy to miss some links, causing visitors to see errors or old pages.

Every time you want to change something, you must hunt through your code and fix many places.

The Solution

Redirect and rewrite rules let you set simple instructions in one place.

These rules automatically send visitors to the right pages or change URLs behind the scenes.

This keeps your site working smoothly without changing every link manually.

Before vs After

✗ Before

Change every link in HTML and JavaScript files manually

✓ After

firebase.json with redirect and rewrite rules configured"

What It Enables

You can easily manage URL changes and user navigation without touching your entire website code.

Real Life Example

Your company rebrands and changes product page URLs.

Instead of updating thousands of links, you add redirect rules so old URLs automatically send visitors to new pages.

Key Takeaways

Manual URL changes are slow and error-prone.

Redirect and rewrite rules automate URL management.

This keeps websites user-friendly and easy to update.

Practice

1. What is the main difference between a redirect and a rewrite in Firebase Hosting?

easy

A. Redirect changes the browser URL, rewrite does not change the URL shown.

B. Rewrite changes the browser URL, redirect does not change the URL shown.

C. Both redirect and rewrite always change the browser URL.

D. Neither redirect nor rewrite affect the browser URL.

Solution

1. Step 1: Understand redirect behavior

   A redirect sends the user to a new URL and updates the browser address bar to show this new URL.

2. Step 2: Understand rewrite behavior

   A rewrite serves different content but keeps the original URL visible in the browser address bar.

3. Final Answer:

   Redirect changes the browser URL, rewrite does not change the URL shown. -> Option A

4. Quick Check:

   Redirect updates URL, rewrite keeps URL same [OK]

Hint: Redirect changes URL, rewrite hides content change [OK]

Common Mistakes:

• Confusing redirect with rewrite behavior
• Thinking rewrite changes browser URL
• Assuming redirect does not update URL

2. Which of the following is the correct Firebase Hosting syntax to redirect from /old-page to /new-page?

easy

A. "redirect": [{"source": "/old-page", "destination": "/new-page"}]

B. "rewrites": [{"source": "/old-page", "destination": "/new-page"}]

C. "rewrites": [{"source": "/old-page", "type": 301, "destination": "/new-page"}]

D. "redirects": [{"source": "/old-page", "destination": "/new-page", "type": 301}]

Solution

1. Step 1: Identify redirect syntax

   Redirects require a source, destination, and a type (like 301 for permanent redirect).

2. Step 2: Check options for correct syntax

   "redirects": [{"source": "/old-page", "destination": "/new-page", "type": 301}] correctly includes source, destination, and type 301. Others miss type or use rewrites incorrectly.

3. Final Answer:

   "redirects": [{"source": "/old-page", "destination": "/new-page", "type": 301}] -> Option D

4. Quick Check:

   Redirect needs type code like 301 [OK]

Hint: Redirects need a type code (301 or 302) [OK]

Common Mistakes:

• Omitting the redirect type code
• Using rewrites instead of redirects for URL change
• Placing type in rewrites block

3. Given this Firebase Hosting config snippet:

{
  "rewrites": [
    {"source": "/app/**", "destination": "/index.html"}
  ]
}

What happens when a user visits /app/profile?

medium

A. The browser URL stays /app/profile but serves content from /index.html.

B. The browser URL changes to /index.html and shows that page.

C. The browser URL changes to /app/index.html and shows that page.

D. The browser returns a 404 error because /app/profile does not exist.

Solution

1. Step 1: Understand rewrite with wildcard

   The rewrite rule matches any URL starting with /app/ and serves /index.html content without changing the URL.

2. Step 2: Apply to /app/profile

   Visiting /app/profile triggers the rewrite, so content from /index.html is served but URL remains /app/profile.

3. Final Answer:

   The browser URL stays /app/profile but serves content from /index.html. -> Option A

4. Quick Check:

   Rewrite serves content without URL change [OK]

Hint: Rewrite serves content but keeps URL same [OK]

Common Mistakes:

• Thinking rewrite changes the URL
• Expecting 404 error for unmatched files
• Assuming redirect happens instead of rewrite

4. You wrote this Firebase Hosting config:

{
  "redirects": [
    {"source": "/home", "destination": "/index.html"}
  ]
}

But the redirect does not work as expected. What is the problem?

medium

A. Using redirects instead of rewrites for serving index.html.

B. The source path should be /home/** to match all subpaths.

C. Missing the redirect type (301 or 302) in the redirect rule.

D. The destination should be a full URL, not a relative path.

Solution

1. Step 1: Analyze the redirect behavior

   A redirect requires a type (301 or 302) to work properly. Missing the type causes the redirect to fail.

2. Step 2: Identify the likely expectation and fix

   Adding the redirect type (301 or 302) will fix the redirect. Using rewrites is an alternative if you want to serve content without changing the URL.

3. Final Answer:

   Missing the redirect type (301 or 302) in the redirect rule. -> Option C

4. Quick Check:

   Redirect requires type code [OK]

Hint: Redirects need a type code (301 or 302) [OK]

Common Mistakes:

• Using redirects instead of rewrites to preserve URL
• Confusing redirects with rewrites
• Using relative paths incorrectly

5. You want to support a single-page app on Firebase Hosting where all URLs under /app/ show index.html content without changing the URL, but also redirect /old-app permanently to /app/. Which config snippet correctly achieves this?

hard

A. {
"rewrites": [
{"source": "/old-app", "destination": "/app/"},
{"source": "/app/**", "destination": "/index.html"}
]
}

B. {
"redirects": [
{"source": "/old-app", "destination": "/app/", "type": 301}
],
"rewrites": [
{"source": "/app/**", "destination": "/index.html"}
]
}

C. {
"redirects": [
{"source": "/old-app/**", "destination": "/app/", "type": 302}
],
"rewrites": [
{"source": "/app/**", "destination": "/index.html"}
]
}

D. {
"redirects": [
{"source": "/old-app", "destination": "/index.html", "type": 301}
],
"rewrites": [
{"source": "/app/**", "destination": "/app/"}
]
}

Solution

1. Step 1: Redirect /old-app to /app/ permanently

   Use a redirect with type 301 from /old-app to /app/ to update browser URL.

2. Step 2: Rewrite all /app/** URLs to serve index.html without changing URL

   Use a rewrite rule matching /app/** to serve /index.html content while keeping URL unchanged.

3. Step 3: Verify option correctness

   { "redirects": [ {"source": "/old-app", "destination": "/app/", "type": 301} ], "rewrites": [ {"source": "/app/**", "destination": "/index.html"} ] } correctly combines a 301 redirect and a rewrite for SPA support. Others misuse rewrites or redirect types.

4. Final Answer:

   { "redirects": [ {"source": "/old-app", "destination": "/app/", "type": 301} ], "rewrites": [ {"source": "/app/**", "destination": "/index.html"} ] } -> Option B

5. Quick Check:

   Redirect updates URL, rewrite serves SPA content [OK]

Hint: Redirect for URL change, rewrite for SPA content [OK]

Common Mistakes:

• Using rewrite instead of redirect for URL change
• Missing redirect type or using wrong type
• Rewriting to wrong destination path