Legacy Browser EOL Migration Checklist

A migration checklist for dropping end-of-life browser support. It covers analytics-based decisions, baseline policy, build-target updates, graceful degradation, and post-launch monitoring.

Estimated Time

4-8 hours

Type

cutover

When to Use This Checklist

Use this checklist when dropping support for end-of-life (EOL) browsers, such as legacy versions that no longer receive updates. Removing them lets you ship modern JavaScript and CSS, shrink bundles by dropping polyfills, and reduce test surface. The risk is alienating real users, so plan the change with data.

How to Use This Checklist

Start with analytics. Quantify how much traffic and revenue still come from EOL browsers before deciding to drop them. A baseline policy should be a business decision informed by real numbers, not just an engineering preference.

Once the baseline is set, capture the technical win. Audit polyfills and transpilation targets tied to old browsers, then update build targets to the new baseline; this often produces a meaningful bundle-size and performance improvement. Replace legacy APIs and vendor-prefixed CSS that the new baseline makes unnecessary.

Protect affected users. Show a clear upgrade message to unsupported browsers, ensure critical flows degrade gracefully, and test across the new matrix. After launch, watch error rates and conversions for affected segments so you can react if the impact is larger than expected.

What Good Looks Like

The decision is backed by analytics, a supported-browser policy is documented, and build targets match the new baseline for a smaller bundle. Unsupported browsers see a clear upgrade message, critical flows degrade gracefully, and the new matrix is tested. Post-launch monitoring tracks error rates and conversions for affected segments.

Common Pitfalls

The biggest pitfall is dropping browsers without data and silently losing a meaningful user segment. Teams also remove polyfills but forget to update build targets, leaving the bundle bloated and the win unrealized. Shipping no upgrade message leaves affected users staring at a broken page with no explanation.

Related Resources

Use progressive enhancement and responsive web design to degrade gracefully, performance budgets to capture the bundle win, and feature flags to stage the change. Keep WCAG 2.2 conformance on the new baseline.

See a real scan run

A replay of the actual CLI running against our test repositories — live progress, real findings, a genuine DriftScore. Nothing executes in your browser.

Replay

demo@vibgrate — bash

❯ npx @vibgrate/cli scan

╭──────────────────────────────────────────╮

│ Vibgrate Drift Report │

╰──────────────────────────────────────────╯

── node-turborepo (node) .

Runtime: >=18.0.0 (6 majors behind)

Frameworks:

Turbo: 1.13.4 → 2.10.12 (1 behind)

TypeScript: 5.9.3 → 7.0.2 (2 behind)

Dependencies:

1 current 1 1-behind 3 2+ behind 1 unknown

── @repo/admin (node) apps/admin

Frameworks:

TanStack Query: 5.102.5 → 5.102.5 (current)

React: 18.3.1 → 19.2.8 (1 behind)

React DOM: 18.3.1 → 19.2.8 (1 behind)

TypeScript: 5.9.3 → 7.0.2 (2 behind)

Vite: 5.4.21 → 8.2.2 (3 behind)

Dependencies:

3 current 9 1-behind 3 2+ behind 4 unknown

── @repo/api (node) apps/api

Frameworks:

Express: 4.22.2 → 5.2.1 (1 behind)

TypeScript: 5.9.3 → 7.0.2 (2 behind)

Vitest: 1.6.1 → 4.1.11 (3 behind)

Dependencies:

7 current 5 1-behind 3 2+ behind 4 unknown

── @repo/web (node) apps/web

Frameworks:

Next.js: 14.2.35 → 16.3.3 (2 behind)

React: 18.3.1 → 19.2.8 (1 behind)

React DOM: 18.3.1 → 19.2.8 (1 behind)

TypeScript: 5.9.3 → 7.0.2 (2 behind)

Dependencies:

2 current 6 1-behind 3 2+ behind 5 unknown

── @repo/config (node) packages/config

Frameworks:

TypeScript: 5.9.3 → 7.0.2 (2 behind)

Dependencies:

2 current 2 1-behind 5 2+ behind 0 unknown

── @repo/database (node) packages/database

Frameworks:

Prisma: 5.22.0 → 7.10.0 (2 behind)

TypeScript: 5.9.3 → 7.0.2 (2 behind)

Dependencies:

1 current 0 1-behind 3 2+ behind 1 unknown

── @repo/types (node) packages/types

Frameworks:

TypeScript: 5.9.3 → 7.0.2 (2 behind)

Dependencies:

0 current 0 1-behind 1 2+ behind 1 unknown

── @repo/ui (node) packages/ui

Frameworks:

React: 18.3.1 → 19.2.8 (1 behind)

TypeScript: 5.9.3 → 7.0.2 (2 behind)

React: 18.3.1 → 19.2.8 (1 behind)

Dependencies:

1 current 4 1-behind 1 2+ behind 1 unknown

── @repo/utils (node) packages/utils

Frameworks:

TypeScript: 5.9.3 → 7.0.2 (2 behind)

Vitest: 1.6.1 → 4.1.11 (3 behind)

Dependencies:

0 current 1 1-behind 2 2+ behind 1 unknown

Tech Stack

Frontend: React, React DOM

Meta-frameworks: Next.js

Bundlers: tsx, Turbo, Vite

CSS / UI: Autoprefixer, PostCSS, Tailwind CSS

Backend: Express

ORM / Database: Prisma, Prisma Client

Testing: Vitest

Lint & Format: ESLint, ESLint Prettier, ESLint React, Prettier, typescript-eslint

Services & Integrations

Auth: JWT 9.0.3

Databases: Prisma 5.22.0

TypeScript

v5.3.3 · strict ✔ · MIXED · target: ES2022

Build & Deploy

Package Managers: pnpm

Monorepo: npm-workspaces, pnpm-workspaces, turbo

Product Purpose Signals

Frameworks: react, nextjs

Evidence: 177

Top Signals:

- [heading] Dashboard (apps/admin/src/pages/Dashboard.tsx)

- [title] Revenue Overview (apps/admin/src/pages/Dashboard.tsx)

- [copy] workspace:* (packages/ui/package.json)

- [copy] ./dist (packages/ui/tsconfig.json)

- [copy] ./src/index.ts (packages/ui/package.json)

- [copy] @repo/config/tsconfig-base.json (packages/ui/tsconfig.json)

- [copy] @repo/ui (packages/ui/package.json)

- [copy] #3b82f6 (apps/admin/src/pages/Dashboard.tsx)

Unknowns:

- No pricing or billing evidence found.

- No integrations/connectors evidence found.

- No route structure evidence found.

Security Posture

Lockfile ✖ · .env ✔ · node_modules ✔

Platform

Native modules: turbo

Code Quality

Files: 36 · Functions: 183 · Avg complexity: 2.62 · Avg length: 21.13 lines

Max nesting: 2 · Circular deps: 0 · Dead code: 0%

God files: apps/admin/src/pages/Products (448 lines)

Database Schema

postgresql · 8 models · 1 enum

Models: Address, CartItem, Category, Order, OrderItem (+3 more)

Findings (16 errors, 11 warnings)

✖ Node.js runtime ">=18.0.0" reached end-of-life on 2025-04-30 (latest: 24.0.0).

vibgrate/runtime-eol in .

⚠ TypeScript is 2 major versions behind (current: 5.9.3, latest: 7.0.2).

vibgrate/framework-major-lag in .

✖ 60% of dependencies are 2+ major versions behind in node-turborepo.

vibgrate/dependency-rot in .

✖ @types/node is 6 major versions behind (spec: ^20.11.0, latest: 26.3.0).

vibgrate/dependency-major-lag in .

⚠ TypeScript is 2 major versions behind (current: 5.9.3, latest: 7.0.2).

vibgrate/framework-major-lag in apps/admin

✖ Vite is 3 major versions behind (current: 5.4.21, latest: 8.2.2).

vibgrate/framework-major-lag in apps/admin

✖ vite is 3 major versions behind (spec: ^5.0.12, latest: 8.2.2).

vibgrate/dependency-major-lag in apps/admin

⚠ TypeScript is 2 major versions behind (current: 5.9.3, latest: 7.0.2).

vibgrate/framework-major-lag in apps/api

✖ Vitest is 3 major versions behind (current: 1.6.1, latest: 4.1.11).

vibgrate/framework-major-lag in apps/api

✖ @types/node is 6 major versions behind (spec: ^20.11.0, latest: 26.3.0).

vibgrate/dependency-major-lag in apps/api

✖ vitest is 3 major versions behind (spec: ^1.2.1, latest: 4.1.11).

vibgrate/dependency-major-lag in apps/api

⚠ Next.js is 2 major versions behind (current: 14.2.35, latest: 16.3.3).

vibgrate/framework-major-lag in apps/web

⚠ TypeScript is 2 major versions behind (current: 5.9.3, latest: 7.0.2).

vibgrate/framework-major-lag in apps/web

✖ @types/node is 6 major versions behind (spec: ^20.11.0, latest: 26.3.0).

vibgrate/dependency-major-lag in apps/web

⚠ TypeScript is 2 major versions behind (current: 5.9.3, latest: 7.0.2).

vibgrate/framework-major-lag in packages/config

✖ 56% of dependencies are 2+ major versions behind in @repo/config.

vibgrate/dependency-rot in packages/config

✖ eslint-plugin-react-hooks is 3 major versions behind (spec: ^4.6.0, latest: 7.1.1).

vibgrate/dependency-major-lag in packages/config

⚠ Prisma is 2 major versions behind (current: 5.22.0, latest: 7.10.0).

vibgrate/framework-major-lag in packages/database

⚠ TypeScript is 2 major versions behind (current: 5.9.3, latest: 7.0.2).

vibgrate/framework-major-lag in packages/database

✖ 75% of dependencies are 2+ major versions behind in @repo/database.

vibgrate/dependency-rot in packages/database

⚠ TypeScript is 2 major versions behind (current: 5.9.3, latest: 7.0.2).

vibgrate/framework-major-lag in packages/types

✖ 100% of dependencies are 2+ major versions behind in @repo/types.

vibgrate/dependency-rot in packages/types

⚠ TypeScript is 2 major versions behind (current: 5.9.3, latest: 7.0.2).

vibgrate/framework-major-lag in packages/ui

⚠ TypeScript is 2 major versions behind (current: 5.9.3, latest: 7.0.2).

vibgrate/framework-major-lag in packages/utils

✖ Vitest is 3 major versions behind (current: 1.6.1, latest: 4.1.11).

vibgrate/framework-major-lag in packages/utils

✖ 67% of dependencies are 2+ major versions behind in @repo/utils.

vibgrate/dependency-rot in packages/utils

✖ vitest is 3 major versions behind (spec: ^1.2.1, latest: 4.1.11).

vibgrate/dependency-major-lag in packages/utils

╭──────────────────────────────────────────╮

│ Top Priority Actions │

╰──────────────────────────────────────────╯

1. Upgrade EOL runtime in node-turborepo

End-of-life runtimes no longer receive security patches and block ecosystem upgrades.

./.

>=18.0.0 → 24.0.0 (6 majors behind)

Impact: −10 drift points (runtime & EOL)

2. Fix security posture: no lockfile found

Without a lockfile, installs are non-deterministic. Run the install command to generate one and commit it.

Missing: package-lock.json, pnpm-lock.yaml, or yarn.lock

3. Upgrade Vite 5.4.21 → 8.2.2 in @repo/admin (+2 more)

3 major versions behind. Major framework drift increases breaking change risk and blocks access to security fixes and performance improvements.

./apps/admin

Vite: 5.4.21 → 8.2.2 (3 majors behind)

./apps/api

Vitest: 1.6.1 → 4.1.11 (3 majors behind)

./packages/utils

Vitest: 1.6.1 → 4.1.11 (3 majors behind)

Impact: −5–15 drift points

4. Reduce dependency rot in @repo/types (100% severely outdated)

1 of 1 dependencies are 2+ majors behind. Run `npm outdated` and prioritise packages with known CVEs or breaking API changes.

./packages/types

typescript: 5.9.3 → 7.0.2 (2 majors behind)

Impact: −5–10 drift points

5. Reduce dependency rot in @repo/database (75% severely outdated)

3 of 4 dependencies are 2+ majors behind. Run `npm outdated` and prioritise packages with known CVEs or breaking API changes.

./packages/database

@prisma/client: 5.22.0 → 7.10.0 (2 majors behind)

prisma: 5.22.0 → 7.10.0 (2 majors behind)

typescript: 5.9.3 → 7.0.2 (2 majors behind)

Impact: −5–10 drift points

╭──────────────────────────────────────────╮

│ Architecture Layers │

╰──────────────────────────────────────────╯

Archetype: nextjs (80% confidence)

Files classified: 24 (11 unclassified)

Folders classified: 8

apps/admin/src presentation 100% 4 files

apps/admin/src/pages presentation 100% 2 files

apps/api/src/middleware middleware 100% 2 files

apps/api/src/routes routing 100% 2 files

apps/web/src/app presentation 100% 4 files

apps/web/src/app/products presentation 100% 2 files

apps/web/src/app/products/[id] presentation 100% 1 file

packages/ui/src presentation 100% 6 files

Unclassified source (sample): 11

presentation 15 files drift ████████████████████ 100 risk high

routing 4 files drift ████████████████████ 100 risk high

middleware 2 files drift ███████▍░░░░░░░░░░░░ 37 risk moderate

config 2 files drift ░░░░░░░░░░░░░░░░░░░░ 0 risk none

shared 1 file drift ████████████████████ 100 risk high

╭──────────────────────────────────────────╮

│ DriftScore Summary │

╰──────────────────────────────────────────╯

DriftScore: 66/100

Risk Level: HIGH

Projects: 9

Classified: 8 nano · 1 micro · 0 small · 0 standard

Billable: 0.42 · 9 detected → 0.42 billable projects (micro-project pricing)

0.1 micro · 0.32 nano

These fractions add up across repositories, then round down to whole billable projects.

Score Breakdown

Runtime: ████████████████████ 100

Frameworks: █████████▏░░░░░░░░░░ 46

Dependencies: ██████▏░░░░░░░░░░░░░ 31

EOL Risk: ████████████████████ 100

Scanned at 2026-08-26T09:08:28.481Z · 7.1s · 286 files scanned · 56 workspace files · 27 dirs

❯

Press Run to start.

Explore the Vibgrate CLI

Legacy Browser EOL Migration Checklist

When to Use This Checklist

How to Use This Checklist

What Good Looks Like

Common Pitfalls

Related Resources

Tags

See a real scan run