Vercel and Netlify deployment in Svelte - Performance & Optimization

Performance: Vercel and Netlify deployment

MEDIUM IMPACT

This affects the initial page load speed and caching efficiency by how the site is deployed and served from the hosting platform.

Deploying a Svelte app with optimized build and caching

Svelte

Using Vercel or Netlify with SvelteKit's adapter and enabling build optimizations plus caching headers

Assets are pre-built, minified, and cached efficiently, reducing load times and repeated downloads.

📈 Performance GainReduces LCP by up to 50%, enables fast repeat visits with cached assets

Deploying a Svelte app with optimized build and caching

Svelte

Deploying without proper build optimization or caching headers on Netlify or Vercel

This causes slower initial loads and repeated downloads of unchanged assets, increasing LCP and bandwidth use.

📉 Performance CostBlocks rendering longer on first load, increases LCP by 1-3 seconds depending on asset size

Performance Comparison

Pattern	DOM Operations	Reflows	Paint Cost	Verdict
Deploy without build optimization or caching	No change	No change	Higher due to larger assets	[X] Bad
Deploy with SvelteKit adapter and caching on Vercel/Netlify	No change	No change	Lower due to smaller assets and caching	[OK] Good

Rendering Pipeline

Deployment platforms serve pre-built static or server-rendered pages that the browser fetches. Proper caching and CDN usage reduce network delays and speed up the Style Calculation and Paint stages.

→Network Fetch

→Style Calculation

→Paint

⚠️ BottleneckNetwork Fetch due to asset size and caching strategy

Core Web Vital Affected

LCP

This affects the initial page load speed and caching efficiency by how the site is deployed and served from the hosting platform.

Optimization Tips

1Always use SvelteKit adapters for Vercel or Netlify to optimize builds.

2Enable caching headers to leverage CDN and browser caching.

3Compress assets to reduce network transfer size and speed up LCP.

Performance Quiz - 3 Questions

What deployment feature most improves initial load speed for a Svelte app on Vercel or Netlify?

A Deploying without build steps

B Using build optimizations and caching headers

C Uploading uncompressed assets

D Disabling CDN caching

DevTools: Network

How to check: Open DevTools, go to Network tab, reload the page, and check asset sizes and cache status (look for 304 Not Modified or cache hits).

What to look for: Look for small asset sizes, fast load times, and cache hits indicating efficient deployment and caching.

Practice

1. What is the main purpose of using Vercel or Netlify with a Svelte app?

easy

A. To write Svelte code faster using special editors

B. To easily deploy and host the app online with automatic updates

C. To convert Svelte code into plain HTML manually

D. To debug Svelte apps without running them

Solution

1. Step 1: Understand deployment platforms

   Vercel and Netlify are services that host web apps and update them automatically when code changes.

2. Step 2: Connect with Svelte app workflow

   They connect to your Git repo, build your Svelte app, and publish it online without manual steps.

3. Final Answer:

   To easily deploy and host the app online with automatic updates -> Option B

4. Quick Check:

   Deployment = Easy hosting and updates [OK]

Hint: Think: Vercel/Netlify = online hosting + auto updates [OK]

Common Mistakes:

• Confusing deployment with coding or debugging tools
• Thinking they convert code manually
• Assuming they only help with writing code

2. Which of the following is the correct step to deploy a Svelte app on Netlify?

easy

A. Set build command to 'npm run start' and publish directory to 'public'

B. Upload your Svelte files manually without any build settings

C. Connect Git repo and set build command to 'npm run build' with publish directory 'public/build'

D. Connect your Git repository, set build command to 'npm run build', and publish directory to 'build'

Solution

1. Step 1: Identify Netlify build settings for Svelte

   Netlify needs the build command 'npm run build' to compile the app and the publish directory where the built files are stored.

2. Step 2: Know Svelte's default build output

   Svelte outputs built files in 'public/build', so this should be the publish directory.

3. Final Answer:

   Connect Git repo and set build command to 'npm run build' with publish directory 'public/build' -> Option C

4. Quick Check:

   Netlify build = 'npm run build' + 'public/build' [OK]

Hint: Remember: build command builds, publish points to output folder [OK]

Common Mistakes:

• Using 'npm run start' instead of 'npm run build'
• Setting publish directory to 'build' instead of 'public/build'
• Uploading files manually without build

3. Given this Vercel deployment setting for a Svelte app:
Build Command: npm run build
Output Directory: build
What will happen when you push new code to Git?

medium

A. Vercel will build the app and deploy files from the 'build' folder

B. Vercel will fail because the output directory should be 'public/build'

C. Vercel will deploy the app but with old code only

D. Vercel will skip build and deploy source files directly

Solution

1. Step 1: Understand Vercel build and output settings

   Vercel runs the build command to create production files, then deploys from the specified output directory.

2. Step 2: Check if 'build' is valid output directory

   In many Svelte setups, the build output is in 'build' or 'public/build'. If 'build' is correct, deployment succeeds.

3. Final Answer:

   Vercel will build the app and deploy files from the 'build' folder -> Option A

4. Quick Check:

   Build + correct output folder = successful deploy [OK]

Hint: Build command + correct output folder = deploy success [OK]

Common Mistakes:

• Assuming output directory must be 'public/build' always
• Thinking Vercel deploys source files without build
• Confusing build failure with deployment failure

4. You deployed a Svelte app on Netlify but the site shows a 404 error after deployment. What is the most likely cause?

medium

A. The build command is set to 'npm run start' instead of 'npm run build'

B. The Git repository is empty and has no code

C. You forgot to connect your Git repo to Netlify

D. The publish directory is set incorrectly, so Netlify can't find the built files

Solution

1. Step 1: Analyze 404 error cause on Netlify

   A 404 after deployment usually means Netlify can't find the files to serve, often due to wrong publish directory.

2. Step 2: Check common misconfigurations

   If the publish directory is wrong, Netlify deploys an empty or wrong folder, causing 404 errors.

3. Final Answer:

   The publish directory is set incorrectly, so Netlify can't find the built files -> Option D

4. Quick Check:

   404 on deploy = wrong publish directory [OK]

Hint: 404 after deploy? Check publish directory first [OK]

Common Mistakes:

• Assuming empty Git repo causes 404 (usually build fails first)
• Forgetting to connect Git repo (would block deploy)
• Confusing build command with publish directory

5. You want to deploy a Svelte app on Vercel with these requirements:
- Use GitHub repo
- Automatically rebuild on push
- Serve from 'public' folder
Which setup is correct?

hard

A. Connect GitHub repo, set build command 'npm run build', output directory 'public'

B. Connect GitHub repo, set build command 'npm run dev', output directory 'public/build'

C. Connect GitHub repo, set build command 'npm run build', output directory 'public/build'

D. Connect GitHub repo, no build command, output directory 'public'

Solution

1. Step 1: Understand Vercel deployment with GitHub

   Connecting GitHub repo enables automatic rebuilds on push. The build command must create production files.

2. Step 2: Identify correct build command and output folder

   'npm run build' builds the app. To serve from 'public' folder as required, output directory must be 'public'.

3. Final Answer:

   Connect GitHub repo, set build command 'npm run build', output directory 'public' -> Option A

4. Quick Check:

   GitHub + build + 'public' output folder = proper deploy [OK]

Hint: Build with 'npm run build' and output 'public' [OK]

Common Mistakes:

• Using 'npm run dev' which is for local development
• Setting output directory to 'public/build' instead of 'public'
• Skipping build command causing no production files