Roughly once a month someone asks me to "make their Squarespace site headless", and most of the time they are not sure what they are actually asking for. Squarespace is a closed system that does a lot for you in exchange for staying inside its walls. Pulling a site out of it onto a headless setup is less a migration and more a rebuild, plus quietly taking over the dozen jobs Squarespace was handling in the background. I have done a few of these now, so here is the honest version before you spend the money.
Why people actually leave Squarespace
Squarespace is good at what it is for. If you have a brochure site or a small blog and it looks fine, you should probably stay. The real reasons people outgrow it are specific: they have hit the ceiling on design and layout and are tired of fighting the template, the site feels slow and heavy and they can do little about it, they need a proper content model instead of "pages and blog posts" so the same content can feed a website and an app and a newsletter, or they want a real development workflow with version control instead of clicking around inside an editor. "Headless sounds modern" is not a reason. Work out which of those is true for you first.
What "headless" means in this case
Headless just means your content lives in one place and a separate frontend renders it over an API. With Squarespace there is an extra wrinkle people miss: Squarespace is not really built to be a headless backend, and it has no proper content API meant for this. So in practice you are not keeping Squarespace as the brain and bolting a new frontend on. You are moving the content into an actual headless CMS, then building the frontend (I reach for Nuxt) on top of that. It is a full move, not a halfway house, and that gap is the thing people underestimate.
Getting your content out is the first surprise
Squarespace's export is thin. You get a WordPress-format XML file that covers pages and blog posts and not a great deal else. Galleries, product data, event collections, custom layouts, form submissions and most of your design choices do not come with it. For a simple blog that export is enough to script an import. For anything richer you are looking at a mix of the export, whatever the platform will hand back, and a fair amount of careful copy and paste. I audit the real site page by page before quoting, because the export almost never tells the whole story.
The things Squarespace quietly did for you
This is where the work actually lives. Hosting and the CDN, automatic image resizing, contact and booking forms, SSL, the basic SEO fields, scheduled publishing, and if you ran a shop, the whole checkout and payments stack. None of that stops being a need just because you left. Each one becomes something you rebuild, wire up to a third-party service, or decide you can live without. Forms are the one people forget every time: on Squarespace a contact form just works, and on a custom frontend somebody has to build the endpoint, the spam handling and the email that actually tells you a lead came in.
Do not throw away your search rankings
Squarespace has its own URL patterns, with blog posts sitting under /blog/ and dated paths and so on. The day you launch a new structure without a redirect map, you hand back every ranking you had. Map every old URL to its new home with 301 redirects, carry over your page titles and meta descriptions, keep your structured data, and submit the new sitemap. This part is dull and it is the single most important hour of the whole project. I have watched people launch a lovely fast new site and lose half their traffic for a month because nobody did the redirects.
The speed promise you have to actually keep
The usual reason for doing this is speed, so the one outcome you cannot accept is launching and being slower. It happens more than you would think. A sloppy headless rebuild can ship more JavaScript than the Squarespace template it replaced. Measure Core Web Vitals on the old site before you start, build the new one to ship only what each page needs, and measure again before you call it finished. Do not trust the assumption that new automatically means fast, including when that assumption is coming from me.
So should you do it?
For most small Squarespace sites, no. Stay where you are and put the money into the actual business. It becomes worth it when you have genuinely hit the design or structure ceiling, when you need a real content model that more than one thing can read from, or when performance and ownership matter enough to justify both the build and the ongoing upkeep, because you are taking on jobs Squarespace used to do for free. Going headless is a trade, not a free upgrade: more control and more speed in return for owning more of the machine.
If you are weighing it up, the same logic applies whatever you are leaving. I have written the Shopify version of this, and the longer story of why I moved my own work off Magento to headless. If you want someone to scope it honestly, that is what the services page is for. Either way, go in knowing what you are signing up for.