# HubSpot Submit Form API sets hidden fields blank

**URL:** <https://community.hubspot.com/t/hubspot-submit-form-api-sets-hidden-fields-blank/143902>\
**Category:** APIs & Integrations\
**Tags:** third-party-apps\
**Created:** [December 10, 2025, 10:04pm UTC](https://community.hubspot.com/t/hubspot-submit-form-api-sets-hidden-fields-blank/143902 "2025-12-10T22:04:47Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![JMarfleet](https://avatars.discourse-cdn.com/v4/letter/j/977dab/32.png) [@JMarfleet](https://community.hubspot.com/u/JMarfleet)\
**Post date:** [December 10, 2025, 10:04pm UTC](https://community.hubspot.com/t/hubspot-submit-form-api-sets-hidden-fields-blank/143902/1 "2025-12-10T22:04:47Z")

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In a Hubspot Form, I’ve added certain hidden fields with default values. In my api call I do not specifiy these fields. However, these fields are blank on the Contact when I submit the API call. Why is this?

 ![JMarfleet_0-1765403914909.png](https://d2qpr2jzcazej7.cloudfront.net/original/2X/a/a17269537c00a0b8e1563df79c9fce46c3861631.png)

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**Author:** ![TomM2](https://d10pqhm3lwygmk.cloudfront.net/user_avatar/community.hubspot.com/tomm2/32/70887_2.png) [@TomM2](https://community.hubspot.com/u/TomM2)\
**Post date:** [December 11, 2025, 10:43am UTC](https://community.hubspot.com/t/hubspot-submit-form-api-sets-hidden-fields-blank/143902/2 "2025-12-11T10:43:59Z")

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Hey @JMarfleet the HubSpot form editor doesn’t affect an api submission at all, it’s just a frontend editor for creating HubSpot forms. If you’re submitting via the api adding or updating anything on the form editor won’t add these fields to your api submission. You’ll need to send the field values via your api submission to have these populate within the submission.

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<div class="post-metadata">

**Author:** ![JMarfleet](https://avatars.discourse-cdn.com/v4/letter/j/977dab/32.png) [@JMarfleet](https://community.hubspot.com/u/JMarfleet)\
**Post date:** [December 11, 2025, 2:24pm UTC](https://community.hubspot.com/t/hubspot-submit-form-api-sets-hidden-fields-blank/143902/3 "2025-12-11T14:24:13Z")

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Hi @TomM2 !  
Thank you for the quick reply. We did just that. It does make it slightly harder to maintain as we have to maintain the default values on every api that calls that form. Appreciate the clarification.

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**Author:** ![RubenBurdin](https://d10pqhm3lwygmk.cloudfront.net/user_avatar/community.hubspot.com/rubenburdin/32/75212_2.png) [@RubenBurdin](https://community.hubspot.com/u/RubenBurdin)\
**Post date:** [December 16, 2025, 8:19pm UTC](https://community.hubspot.com/t/hubspot-submit-form-api-sets-hidden-fields-blank/143902/4 "2025-12-16T20:19:18Z")

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Hi @JMarfleet , yep, this one bites a lot of folks the first time. “Default values” and “hidden fields” you set in the form editor are really for HubSpot’s own rendered form experience, not for API submissions. When you submit via the Forms API, HubSpot will only process what you explicitly send in the payload. If a field isn’t included, HubSpot won’t magically apply the editor default for it, and if you include it with an empty value, it can effectively clear it.

The behavior is consistent with the submit endpoint docs, where the submission is just the list of fields you pass in ([Accounts Dashboard | HubSpot](https://developers.hubspot.com/docs/api-reference/legacy/forms-v3-legacy/post-submissions-v3-integration-secure-submit-portalId-formGuid)).

If maintaining the same defaults across multiple callers is the pain, the usual pattern is to keep those defaults in one place in your middleware (env vars or a tiny config file) and have every submit call merge them in before POSTing to HubSpot. Another option, if you have access to workflows, is to set those properties after submission when they’re empty and the submission came from that form, so your API can stay minimal and HubSpot enforces the defaults centrally ([Accounts Dashboard | HubSpot](https://developers.hubspot.com/docs/api-reference/marketing-forms-v3/guide)).