A phased roadmap for frontend modernization

A migration works when every phase has a clear output and someone decides whether to continue. This template gives you the phases, the exit criteria and the governance around them.

How to use this template

The roadmap has four stages. Each one ends with a checkpoint where a named person decides whether to continue, adjust or stop. Copy the structure, replace the examples with your modules and attach dates once the assessment gives you real data.

Stage 1: Assessment

Activities

• Inventory of screens, routes, services and third-party libraries, with usage data.
• Review of tests, build chain and deployment process.
• Choice of approach: rewrite, hybrid or micro-frontends. See how to choose.
• Choice of the pilot module.
• Draft of the phases with a rough size for each.

Exit criteria

• Every screen is listed and marked as migrate, delete or leave.
• Every third-party widget has a decision.
• The pilot has a scope and a definition of done.

Stage 2: Pilot

Activities

• Set up the hybrid application or the shell.
• Share authentication and session between old and new code.
• Make old and new routes coexist.
• Migrate one real screen and release it behind a switch.
• Set up the end-to-end tests for the critical flows.

Exit criteria

• The screen is live for all users and the legacy version is deleted.
• A rollback was rehearsed at least once.
• The effort was recorded and the phase estimates were recalibrated with it.

Stage 3: Migration phases

Group the screens into phases that make sense to the business, usually by module. A good phase is small enough to finish in weeks and large enough to deliver something a stakeholder recognizes.

How to order the phases

1. Shared services and the pieces many screens depend on.
2. Modules with low risk and clear boundaries, to build rhythm.
3. Modules with planned feature work, so new features land on new code.
4. The busiest and most complex modules, once the patterns are proven.
5. The shell: navigation, layout and login, when convenient.

Definition of done for each screen

• Same behavior as the legacy version, verified by tests or a parity review.
• Live for all users.
• Legacy code and its feature flag removed.

Exit criteria for each phase

• All screens in the phase meet the definition of done.
• No open regression of high severity.
• The forecast for the remaining phases is updated.

The technical steps inside a phase are described in How to migrate AngularJS to Angular without downtime.

Stage 4: Cleanup

• Remove the legacy framework and its libraries from the dependencies.
• Delete the compatibility layer, the legacy router and leftover flags.
• Simplify the build and the pipeline.
• Update the documentation and the onboarding guide.
• End any extended support subscription.

A migration without this stage leaves a hybrid that lives for years. Put it in the plan and in the budget from day one.

Governance

Roles

• Sponsor. Owns the budget and makes the checkpoint decisions.
• Product owner. Answers questions about behavior and accepts each screen.
• Technical lead. Owns the approach and the quality rules.
• Migration lead. Runs the day-to-day work and reports progress. This can be an internal person or an external partner.

Rules that keep the roadmap honest

• No redesign inside the migration. Changes to layout or behavior go to the product backlog.
• New screens are built only on the new stack.
• A screen counts as migrated only when its legacy version is deleted.
• Scope changes go through the sponsor at a checkpoint.

Checkpoints

The metrics for the monthly report are covered in measuring migration progress.

More in this section

• How to choose a frontend migration partner
• Frontend migration risks and how to reduce them
• The strangler fig pattern applied to frontends
• Feature flags and route switches in an incremental migration