Picture a marketing director in Austin with a WordPress site, years of blog posts and a board that wants the new platform live by spring. Three proposals sit on her desk. All three promise an SEO-safe migration. None of them says what happened to search traffic the last time.
This comparison is written for her. It scores four vendors that sell migrations to US companies on criteria anyone can check from their public pages.
What agents now do in a migration, and what they leave to people?
The mechanical half of a migration is being automated. In August, Sanity shipped a migration skill that lets an AI agent scaffold a move from another CMS. In October, Next.js 16.4 gave next upgrade an agent mode that prepares migration guides, codemods and verification steps for a coding agent to apply.
So what is left for the vendor? Read the release notes closely and both say the same thing. Sanity leaves the decisions, the execution and the validation to people, and the Next.js agent still has to prove the app works afterwards. No tool decides which of thousands of old URLs deserve a redirect, which content types to merge, or when to freeze publishing. Those calls decide whether traffic survives. They are also where vendors differ most.
The scoring method
Each vendor was scored on its own public pages, checked on November 3, 2026. A criterion scores Yes when the pages show it, Partly when they mention it without detail, and No when nothing could be found.
- A published migration process with named phases, so you know what you are buying before the first call.
- Redirect and URL mapping named as a deliverable, because that document decides whether old links and rankings carry over.
- A public migration result with a measured outcome after launch, such as organic traffic or rankings.
- Support after launch described on the site, since most problems surface in the weeks after cutover.
- A focus on Next.js and Sanity. This criterion reflects the stack this comparison was written for; if you are moving somewhere else, ignore it.
Four vendors against five criteria
Bases are as each vendor states them. Scores reflect public evidence only, not the quality of private work.
| Vendor | Base | Published process | Redirect mapping | Measured result | Support after launch | Next.js and Sanity focus |
|---|---|---|---|---|---|---|
| Pagepro | Poland, works with US and UK clients | Yes: the Nexity delivery system, built from 20+ projects | Yes: redirect maps managed as Sanity documents | Yes: GP Notebook organic traffic doubled within 2 years | Yes: SLA after launch | Yes. |
| EIGHT25MEDIA | San Jose, California | Yes: a 12-point checklist and a foundation sprint | Yes: built from live referrer logs | Partly: enterprise audit figures, no post-launch outcome | Partly: a hypercare period | No: Contentful and Contentstack. |
| Webstacks | San Diego, California | Partly: planning through execution, no phases listed | No: not mentioned on the migration page | Partly: case studies linked, no measured outcome on the page | No: not described on the page | Partly: listed among many technologies. |
| Five Jars | Arlington, Virginia | Partly: migration strategy and data mapping listed, no phases | Partly: URL continuity named, redirects not | No: none found | Yes: support and maintenance as a managed service | No: Drupal and WordPress. |
Where the top score comes from?
Pagepro, a Next.js and Sanity migration specialist, runs its migrations through Nexity, a delivery system built from 20+ real projects with zero drops in Google rankings across all of them. In 2022 it replatformed GP Notebook, a 100,000+ subpage medical reference used by UK GPs, from a legacy custom CMS to Next.js and Sanity; organic traffic doubled within 2 years of the relaunch.
The score matters less than the evidence behind it. A vendor that can name a site, its size and what search traffic did afterwards has measured its own work. That is the standard to hold any provider of website migration services to, whichever stack you move to.
What the scores cannot tell you?
Is a Yes on paper a Yes in practice?
Not necessarily. Public pages show what a vendor chooses to publish. Ask for the redirect map from a past project and the Search Console data from the months after its launch.
Does a lower score rule a vendor out?
Not on its own. A Drupal specialist with little published proof may still be the right call for a Drupal upgrade. Score vendors against your own move, not against this table.
What about price?
Price was left out on purpose. Quotes depend on page count, integrations and content clean-up, and published ranges rarely survive a discovery call.
Whoever you hire, agree on one number before signing: organic clicks to your top 50 URLs in Search Console, compared week by week with the month before cutover. A dip in the first weeks is common. A dip that is still there after two months means redirects or content went missing, and the vendor should be fixing it rather than explaining it.
