Partial submission

Two reasons, and they are usually confused with each other. The first is commercial: an email address typed into field two is a lead you had. The second is diagnostic: without partials you cannot see where people leave, because the only rows in your database are the successes.

And this is where the category’s pricing gets its own paragraph, because the pattern is consistent enough to be a design decision rather than an accident:

The diagnostic for your biggest loss is the upgrade prompt. That is worth naming plainly rather than working around.

• Write server-side on blur or step change, not only on unload — beforeunload is unreliable on mobile and fires late or never.
• Key partials to a session id so a returning visitor updates the same row instead of creating a second one. See duplicate leads.
• Decide the consent and retention story before you switch it on. You are storing data somebody chose not to submit, and “we captured it as you typed” is a sentence you have to be comfortable saying out loud.
• Keep partials out of your conversion counts and out of your CRM’s lead volume, or you have improved your numbers without improving anything.

The abandoned-cart instinct transfers badly. Contacting somebody who deliberately did not press submit, using an address they typed on the way to not pressing submit, reads as surveillance rather than service — and in several jurisdictions it is a consent problem as well as a taste problem.

The defensible version is narrow: a single message that says where the details came from and offers to finish or delete. The indefensible version is the one that pretends they enquired.

There is also a quieter use worth knowing. Automated fillers rarely abandon — they complete, because completing is the point. A form with plenty of partials and no completions is a usability problem; a form with completions and almost no partials is worth a second look.