Generating public URLs in Supabase

Introduction

We create public URLs to share files stored in the cloud easily. This lets anyone access the file without needing special permissions.

You want to share an image stored in your cloud storage with friends or users.

You need to provide a link to a document for download on your website.

You want to embed a video hosted in your cloud storage into a blog post.

You want to let users preview files without logging in.

You want to send a file link via email or chat quickly.

Syntax

Supabase

const { data, error } = await supabase.storage.from('bucket').getPublicUrl('path/to/file.jpg')

bucket is the name of your storage container.

path/to/file.jpg is the file's location inside the bucket.

Examples

Gets a public URL for the file user123.png inside the avatars bucket.

Supabase

const { data, error } = supabase.storage.from('avatars').getPublicUrl('user123.png')

Generates a public URL for a PDF report stored in a folder inside the documents bucket.

Supabase

const { data, error } = supabase.storage.from('documents').getPublicUrl('reports/2024-summary.pdf')

Sample Program

This code connects to Supabase storage, then gets a public URL for the file vacation/photo1.jpg inside the photos bucket. It prints the URL or an error message.

Supabase

import { createClient } from '@supabase/supabase-js'

const supabaseUrl = 'https://xyzcompany.supabase.co'
const supabaseKey = 'public-anonymous-key'
const supabase = createClient(supabaseUrl, supabaseKey)

async function getPublicUrl() {
  const { data, error } = supabase.storage.from('photos').getPublicUrl('vacation/photo1.jpg')
  if (error) {
    console.error('Error:', error.message)
    return
  }
  console.log('Public URL:', data.publicUrl)
}

getPublicUrl()

Important Notes

Public URLs allow anyone with the link to access the file, so do not use for sensitive data.

Make sure the bucket or file is set to public access in Supabase storage settings.

If you get an error, check the bucket name and file path carefully.

Summary

Generating public URLs lets you share cloud files easily.

Use getPublicUrl with your bucket and file path.

Always check permissions to keep data safe.

Practice

1. What does the getPublicUrl function in Supabase do?

easy

A. It creates a link that anyone can use to access a file in a bucket.

B. It deletes a file from the storage bucket.

C. It uploads a file to the storage bucket.

D. It encrypts a file before storing it.

Solution

1. Step 1: Understand the purpose of getPublicUrl

   This function is designed to generate a URL that can be shared publicly to access a file stored in Supabase storage.

2. Step 2: Compare options with function behavior

   Only It creates a link that anyone can use to access a file in a bucket. describes creating a public link. Other options describe unrelated actions like deleting, uploading, or encrypting files.

3. Final Answer:

   It creates a link that anyone can use to access a file in a bucket. -> Option A

4. Quick Check:

   Public URL = Link to file [OK]

Hint: Public URLs let anyone access files without login [OK]

Common Mistakes:

• Confusing URL generation with file upload
• Thinking it deletes files
• Assuming it encrypts files automatically

2. Which of the following is the correct way to call getPublicUrl in Supabase to get a public URL for a file named photo.jpg in bucket images?

easy

A. supabase.getPublicUrl('images', 'photo.jpg')

B. supabase.storage.getPublicUrl('images/photo.jpg')

C. supabase.storage.from('images').getPublicUrl('photo.jpg')

D. supabase.storage.from('photo.jpg').getPublicUrl('images')

Solution

1. Step 1: Recall the correct method chaining

   The correct syntax is to select the bucket first with from('bucket_name'), then call getPublicUrl('file_path').

2. Step 2: Match options with correct syntax

   supabase.storage.from('images').getPublicUrl('photo.jpg') matches this pattern exactly. Options A, B, and D misuse method calls or argument order.

3. Final Answer:

   supabase.storage.from('images').getPublicUrl('photo.jpg') -> Option C

4. Quick Check:

   Bucket then file path = Correct call [OK]

Hint: Use .from(bucket).getPublicUrl(file) syntax [OK]

Common Mistakes:

• Calling getPublicUrl directly on storage
• Swapping bucket and file arguments
• Using wrong method names

3. What will be the output of this code snippet?

const { data } = supabase.storage.from('docs').getPublicUrl('file.txt');
console.log(data.publicUrl);

medium

A. A boolean indicating if the file exists.

B. A string URL to access 'file.txt' publicly in 'docs' bucket.

C. Undefined because 'data' is not returned by getPublicUrl.

D. An error because getPublicUrl returns a promise.

Solution

1. Step 1: Understand getPublicUrl return value

   The getPublicUrl method returns an object with a publicUrl string property immediately, not a promise.

2. Step 2: Analyze the console.log output

   Logging data.publicUrl will print the URL string to access the file publicly.

3. Final Answer:

   A string URL to access 'file.txt' publicly in 'docs' bucket. -> Option B

4. Quick Check:

   getPublicUrl returns URL string [OK]

Hint: getPublicUrl returns URL object, not a promise [OK]

Common Mistakes:

• Assuming getPublicUrl is async
• Expecting undefined data
• Confusing output with file existence check

4. You tried to generate a public URL with supabase.storage.from('media').getPublicUrl('video.mp4') but got an empty string. What is the most likely cause?

medium

A. getPublicUrl requires an async await call.

B. You forgot to import the Supabase client.

C. The bucket name should be 'videos' not 'media'.

D. The file 'video.mp4' does not exist in the 'media' bucket.

Solution

1. Step 1: Check file existence in bucket

   If the file does not exist, the public URL generated will be empty or invalid.

2. Step 2: Evaluate other options

   Importing client or bucket name mismatch would cause errors, not empty string. getPublicUrl is synchronous, so async is not needed.

3. Final Answer:

   The file 'video.mp4' does not exist in the 'media' bucket. -> Option D

4. Quick Check:

   Missing file = empty URL [OK]

Hint: Empty URL usually means file missing [OK]

Common Mistakes:

• Assuming getPublicUrl is async
• Ignoring file existence
• Mixing up bucket names

5. You want to share a file publicly but keep other files private in the same bucket. Which approach with Supabase storage and getPublicUrl is best?

hard

A. Use getPublicUrl only on files in a public bucket.

B. Set the bucket to private, then generate public URLs only for specific files using getPublicUrl.

C. Make the entire bucket public so all files are accessible.

D. Upload files with a special tag to mark them public.

Solution

1. Step 1: Understand bucket privacy settings

   Supabase storage buckets are either public or private. Public buckets allow all files to be accessed via public URLs.

2. Step 2: Evaluate file-level public access

   Supabase does not support per-file public access in private buckets. To share files publicly, the bucket must be public.

3. Step 3: Choose best practice

   Use getPublicUrl only on files in a public bucket. correctly states to use getPublicUrl on files in a public bucket to share them. Options A and D are incorrect because file-level public control is not supported. Make the entire bucket public so all files are accessible. makes all files public, which is not desired.

4. Final Answer:

   Use getPublicUrl only on files in a public bucket. -> Option A

5. Quick Check:

   Public URLs need public bucket [OK]

Hint: Only public buckets support public URLs per file [OK]

Common Mistakes:

• Thinking private buckets allow public URLs per file
• Making whole bucket public without control
• Assuming tags control public access