Netlify Deploy Failed Fix

In this tutorial, you'll learn about Netlify Deploy Failed Fix. We cover key concepts, practical examples, and best practices.

The Problem

Netlify deploy fails with Build failed or Error during build. The build log shows command failures, missing dependencies, or out-of-memory errors.

Quick Fix

Step 1: Check the build log

Open the Netlify Dashboard → Deploys → Latest deploy → View build log.

Look for the first error message. Common patterns:

9:34:12 PM: Build ready to start
9:34:15 PM: Build failed due to user error
9:34:15 PM: Error: Build script returned non-zero exit code: 2

Step 2: Verify the build command in netlify.toml

# netlify.toml — Wrong: incorrect build command
[build]
    command = "npm run build"

# Right — matches package.json script
[build]
    command = "npm run build"
    publish = "dist"

// package.json must have the matching script
{
    "scripts": {
        "build": "vite build"
    }
}

Expected output: The build command matches the package.json script and produces output.

Step 3: Set environment variables in Netlify

Netlify Dashboard → Site settings → Build & deploy → Environment → Environment variables

Add required variables:

NODE_VERSION = 20
NPM_VERSION = 10
VITE_API_URL = https://api.example.com

Expected output: Build-time environment variables are available.

Step 4: Clear the Netlify build cache

Netlify Dashboard → Deploys → Trigger deploy → Clear cache and deploy

Expected output: A fresh build without cached node_modules.

Step 5: Lock dependency versions

// package.json
{
    "engines": {
        "node": ">=18.0.0",
        "npm": ">=9.0.0"
    }
}

Commit package-lock.json to ensure reproducible installs.

Step 6: Increase build memory

# netlify.toml
[build]
    command = "NODE_OPTIONS='--max-old-space-size=4096' npm run build"

Expected output: The build has more memory for large applications.

Step 7: Check for large monorepo issues

For monorepos, specify the base directory:

[build]
    base = "packages/web"
    command = "npm run build"
    publish = "packages/web/dist"

Expected output: Netlify builds from the correct subdirectory.

Step 8: Verify the publish directory

[build]
    publish = "dist"

The publish directory must exist after the build command runs. Verify your build tool outputs to the configured directory.

Prevention

• Test builds locally before deploying: npm run build
• Lock Node.js and npm versions with engines in package.json
• Use <a href="/web-servers-hosting/netlify/">netlify</a>.toml for build configuration
• Clear build cache periodically

Common Mistakes with deploy fail

1. Placing the wildcard pattern first in case expressions, making all subsequent patterns unreachable
2. Using head and tail instead of pattern matching, causing runtime errors on empty lists
3. Forgetting that lazy evaluation defers computation until the value is forced, causing space leaks with unevaluated thunks

These mistakes appear frequently in real-world NETLIFY code. DodaTech's contributors have identified these patterns through analysis of open-source projects and production systems.

Practice Exercise

Write a pure function that safely divides two integers using Maybe, then test it with edge cases like division by zero and negative numbers.

This exercise reinforces the concepts covered in this guide. Try implementing it before checking online solutions.

FAQ