How to migrate API docs from ReadMe to Mintlify (What works)

Most teams that start a documentation platform migration don't finish it. They underestimate the content audit, hit structural mismatches between platforms, and stall when engineering bandwidth gets pulled back to product work.

The half-migrated portal is the worst outcome you can land in, because it's not a neutral state. You end up with two sources of truth, outdated content split across platforms, and developers who can't tell which version to trust. That actively costs you integrations.

This guide covers what a ReadMe to Mintlify migration actually looks like end to end, based on migrations we've completed for clients like Yuno and Nayax. What breaks, what takes longer than you'd expect, and how to finish the project without pulling your engineering team off their real work.

TL;DR

• Audit your content before touching any platform. Don't migrate garbage.

• Migrate structure first, content second. Design your docs.json navigation before creating pages.

• API reference and conceptual docs need different migration workflows.

• Configure llms-full.txt and analytics before launch, not after.

• Plan for 2-4 weeks of active work minimum. 6-8 weeks if you include design and QA.

Why teams switch from ReadMe to Mintlify

ReadMe is built for API reference management at scale. Mintlify is built for modern developer experience, with more control over structure, design, and search. Teams typically switch when ReadMe stops fitting how they want their docs to look, feel, and behave.

ReadMe does some things well. The interactive API explorer is useful for developers who want to test endpoints without leaving the docs. Built-in versioning works if you're managing a few API versions. And if your docs are mostly auto-generated reference pages, ReadMe handles that without much effort.

The problems tend to show up when your documentation needs grow beyond API reference. ReadMe's guide structure is limited, MDX flexibility is restricted, and customizing the portal's look and navigation gets harder the more opinionated your design requirements are. Cost can also become an issue at higher traffic tiers, especially if you're running a public-facing developer portal that gets significant volume.

Mintlify's appeal comes down to a few specific things. It's Git-native, so your docs live in a repository alongside your code and follow the same review workflow your engineering team already uses. The AI assistant, powered by Claude Sonnet 4 with RAG, gives developers conversational access to your documentation. And llms-full.txt controls how external LLMs index your content, which matters more in 2026 than most teams realize.

Both Yuno and Nayax made this exact switch. In both cases, the decision was driven by the need for a more customizable developer portal that could support structured content beyond just API reference, and that could scale with their documentation as their product lines grew. [Internal Link: GitBook vs ReadMe vs Mintlify comparison -> /blog/gitbook-vs-readme-vs-mintlify-comparison-2026]

What to do before you touch Mintlify

Most migrations fail in planning, not execution. The teams that stall are the ones that jump into Mintlify before they've figured out what they're actually migrating and how it should be organized on the other side.

Run a full content audit

Before you move anything, you need to know what you have. That means inventorying every page in your ReadMe project: URL, title, content type (guide, reference, changelog entry), the last time it was updated, and traffic data if ReadMe's analytics give you access to it.

The goal isn't just a list. It's a triage. Flag content that's outdated and shouldn't be migrated at all, duplicates that should be merged, and gaps where pages are missing and need to be written as part of the migration. The deliverable here is a spreadsheet with a clear migration status for every page before any work starts. It sounds tedious, and it is, but teams that skip this step end up restructuring their portal three or four times after launch.

Map your new navigation structure

Mintlify's docs.json file controls your entire navigation, and if you don't design it before migrating content, you'll rebuild it repeatedly as pages start landing in the wrong places.

A good starting framework: Getting Started, Quickstart, Guides, API Reference, Changelog. That's not a rigid template, but it gives you a skeleton to work from. The important structural decision is separating conceptual docs from reference docs. ReadMe lets these blend together in ways that feel convenient but get messy at scale. Mintlify rewards the separation, and frameworks like Diataxis give you a clear model for how to draw that line. We used it when structuring portals for both CarePortals and Yuno, and it made the rest of the migration significantly smoother.

Decide what gets rewritten vs. what gets ported

Not everything deserves a clean migration. Some content should be copied over as-is, and some should be rewritten during the move.

A reasonable rule of thumb: reference docs can usually be ported directly, especially if they're generated from an OpenAPI spec. Conceptual guides, getting started pages, and tutorials almost always benefit from a rewrite, because the structure that worked in ReadMe won't necessarily work in Mintlify's layout. And if a page was underperforming in ReadMe, migrating it to a better platform won't fix the underlying problem. It'll just underperform with better search.

Set up your Mintlify environment

Get a working local environment and a staging deployment before you start migrating real content. You don't want to discover configuration problems while you're in the middle of porting fifty pages.

Connect your repo and install the CLI

Mintlify is Git-native, so the first step is connecting your GitHub or GitLab repository. Once that's done, install the CLI:

npm i -g

npm i -g

npm i -g

npm i -g

Then run it locally:

Verify that it builds and renders before adding any content. Mintlify auto-deploys on every push to your connected branch, and builds typically take two to three minutes. If something is broken in your base configuration, you want to catch it now.

Configure docs.json before adding pages

docs.json is the control file for your navigation, branding, colors, logos, and metadata. If you're working from older Mintlify documentation or tutorials, you might see references to mint.json, which was the previous name before February 2025.

Set your navigation structure in this file first. Every page you create needs a matching entry in docs.json or it won't appear in your portal. The most common mistake we see is teams adding pages and then trying to build navigation around them afterward. That order is backwards, and it leads to a disorganized portal that needs to be restructured before launch.

Set up your AI and search features

Mintlify's AI assistant uses Claude Sonnet 4 with RAG to give developers conversational answers based on your documentation. It works well, but it needs llms-full.txt configured properly to know what content to index and how.

llms-full.txt also controls how external LLMs like ChatGPT and Claude access and cite your docs. For API-first companies in 2026, this isn't a nice to have. If a developer asks an LLM how to integrate with your product and your docs aren't indexed, the LLM will either hallucinate an answer or point to a competitor's documentation instead. [Internal Link: AI marketing funnel and llms.txt strategy -> /blog/ai-marketing-funnel-llms-txt-strategy]

Set up analytics before launch too. Mintlify tracks visitors, search queries, feedback, and AI assistant usage natively. If you need third-party analytics, connect those before go-live so you have baseline data from day one.

Migrate your content

Migrate in this order: structure, quickstart, core guides, API reference, changelog. Trying to move everything at once is how migrations stall, because you lose track of what's been ported, what's been reviewed, and what still needs work.

Port MDX content from ReadMe

ReadMe exports to Markdown, and since MDX is a superset of Markdown, most content ports without major issues. The things that don't transfer automatically are ReadMe's interactive API explorer widgets, custom embeds, and ReadMe-specific variables. Those need to be replaced with Mintlify's equivalent components: callouts, cards, code groups, steps, and accordions.

After porting, check every internal link. Relative paths change when your navigation structure changes, and broken links are one of the most common post-migration issues. Mintlify's CLI has a broken-links command that catches these, so run it before you consider any batch of pages done.

Migrate your API reference

If you have a clean OpenAPI spec, this is the smoothest part of the migration. Import the spec directly into Mintlify and it generates the reference pages automatically. This is the cleanest path and the one that saves the most time.

If your API reference was hand-written in ReadMe without a backing spec, you have a decision to make: generate a spec now and use it going forward, or continue maintaining the reference manually. The spec route takes more work upfront but pays off every time the API changes, because updates can be generated instead of written by hand. In our experience with Yuno, having a clean OpenAPI spec was what made the API reference migration fast. Teams that don't have one spend significantly more time on this step.

Migrate your changelog

ReadMe changelogs don't export cleanly, so plan to rebuild this section manually. Mintlify uses the <Update /> component with date, title, description, tags, and built-in RSS support.

This is also a good moment to decide on changelog cadence and ownership going forward. The changelog is consistently the section that goes stale fastest after a migration, because nobody has explicitly agreed to own it. If you don't assign an owner now, you'll be looking at an outdated changelog within a couple of months.

Common pitfalls that stall migrations (and how to avoid them)

The same problems show up in almost every ReadMe to Mintlify migration we've seen. All of them are preventable if you plan for them, and all of them are painful if you don't.

• Navigation mismatches: are the most frequent issue. Pages exist in your repo but don't show up in the portal because their file paths don't match what's in docs.json. This happens when someone adds a new page but forgets to update the config, or when file names change during restructuring. Always verify that docs.json entries match file paths exactly.

• Broken internal links: are the second most common problem. Every time you change your navigation structure, links between pages can break. Run mintlify broken-links before launch and again after every structural change. Every broken link is a developer who hits a dead end and either opens a support ticket or gives up.

• OpenAPI spec gaps: tend to surface during migration rather than before it. If your spec is incomplete or hasn't been updated in months, the API reference migration will expose every gap immediately. Fix the spec before you start migrating the reference, not during.

• Ownership gaps after launch: are what cause migrations to lose their value over time. The migration finishes, everyone moves on, and nobody is explicitly responsible for keeping the docs current. Content drifts, and the support volume that dropped after launch starts climbing back up. Assign a clear owner before you go live. [Internal Link: WriteChoice developer portal services -> /services/developer-portals]

• Missing llms-full.txt configuration: is the newest pitfall and the one teams are least likely to think about. If this file isn't configured, LLMs won't index your docs properly. That means developers who ask AI assistants about your product get incomplete or fabricated answers instead of being pointed to your actual documentation.

What a finished migration actually delivers

We've completed two ReadMe to Mintlify migrations, and in both cases the outcomes were measurable within weeks of launch.

Yuno saw adoption increase by more than 50% after the migration. Developers now reach their first successful API call in 15 to 20 minutes. The portal redesign and documentation restructuring also contributed to Yuno winning the Best Payment API Award.

Nayax consolidated documentation for more than 10 products into a single unified portal that now gets over 30,000 monthly visits and 2x more integrations every year.

What drove those results wasn't the platform switch alone. It was the work underneath: a structured content audit before migration, navigation designed around developer workflows, rewritten conceptual guides, clean API reference generated from spec, and clear content ownership after launch. The platform was the enabler, but the content and structure strategy is what made it land.

Key takeaways

• Audit before you migrate. Don't port outdated or underperforming content to a new platform.

• Design navigation in docs.json before adding pages, not after.

• Migrate in order: structure, quickstart, guides, API reference, changelog.

• Configure llms-full.txt and analytics before launch.

• Assign a clear content owner before you go live.

• Expect 2-4 weeks minimum for content-only migrations, and 6-8 weeks if you're including design and QA.

If your team doesn't have the bandwidth to run this end to end, that's the most common reason migrations stall. We've done this twice with measurable results. See how we've handled it or learn more about our developer portal services.