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It’s often the first question asked, even before budget: how long does this take. The honest answer is “it depends,” but that answer deserves to be broken down rather than left vague.
The general range
A Hydrogen headless migration generally takes between 4 and 12 weeks, from the initial audit to the switchover. The range is wide because it depends directly on three factors: the size of the catalogue, the number of third-party integrations to rebuild, and the level of customisation expected on the storefront.
What happens at each stage
Audit (1 to 2 weeks). Analysis of GA4 and Clarity data, a full map of the existing site, mockups of key pages before any development starts. This stage isn’t wasted time: it prevents discovering constraints mid-build that should have been anticipated, and it forms the basis for the final quote.
Staged build (2 to 8 weeks depending on scope). Development of the Hydrogen storefront: product pages, navigation, search, cart, checkout connection. This is the most variable stage in duration. A simple catalogue with little custom business logic builds quickly. A catalogue with configurators, a deep category hierarchy, or specific ERP integrations naturally extends this phase.
Switchover with no downtime (a few days to a week). DNS switchover and SEO redirects, generally carried out during off-peak hours with reinforced monitoring in the following days. This is a short stage in duration but a critical one in preparation: most of the work for this phase actually happens upstream, during the build.
Post-launch support (variable, often 4 weeks included). Performance and conversion adjustments once real traffic is observed on the new version. The first few weeks often reveal optimisations no prior audit could have fully anticipated.
What most often extends the timeline
Poorly documented third-party integrations. An in-house ERP, a marketplace sync, a repricing tool: when these pieces have existed for years without up-to-date documentation, the time needed to understand them before reconnecting them often exceeds initial estimates.
A complex catalogue hierarchy. A deep catalogue with many nested categories requires upfront modelling work, particularly when migrating from a CMS like PrestaShop to Shopify.
Back-and-forth on validation. A client who validates each stage quickly moves faster than a project where every step waits on approval that drags on for days.
What should never be compressed
The time spent on the initial audit and on preparing SEO redirects are the two stages where cutting corners costs the most afterwards. A fast migration that loses 20% of organic traffic because the redirect plan was rushed is never a net time saving, it creates a cleanup project longer than the time saved at the start.
In summary
For a Shopify Liquid to Hydrogen project on a medium-sized catalogue, plan for 6 to 8 weeks. For a CMS to Shopify replatform with a custom ERP and integrations, the range more naturally climbs to 10 to 12 weeks. These are orders of magnitude: the precise quote always depends on the initial audit specific to each site.
To assess the real timeline for your project, the Shopify to Hydrogen migration path details how the initial audit establishes a reliable schedule before any commitment.