Is there a way to update existing records with forms ONLY using AirTable?

Solely using Airtable? No.
But the closest thing you can get is this.

Short answer:

Your #1 best bet for updating Airtable records with a form is to use Fillout’s advanced forms for Airtable.

Long answer:

There is no easy nor reliable way to do this in Airtable on its own.

It requires creating a constantly-changing prefill link for your record (which must be changed every time your record’s data changes), and then you’d have to create an automation to merge the new form submission’s record with the old record, which is especially tricky with linked record fields and attachment fields.

All of this is extremely fragile, difficult to maintain, not secure, and requires using a constantly-updating URL.

Here are the serious & major downsides of trying to use Airtable’s forms to update existing records in Airtable:

1. Critical problem: You will have to continually send out updated prefilled links to your users that always contain the newest data. If the user accidentally clicks on an outdated link, they will be taken to old data in the form. So they would never be able to re-use a link or bookmark a link as an “Update My Account Profile” link.
2. Airtable’s prefilled links do not work with all field types… particularly attachment fields or lengthy long text fields that exceed URL limits.
3. If you need the data to remain private or secure, Airtable’s prefilled links reveal all the data within the link. With Fillout’s links, you get one simple, non-changing link per user that doesn’t reveal any data, and you can even add multiple different layers of security to the form if necessary, including SSO login or email login.
4. Airtable’s prefilled links still won’t update old records… they always create new records, and then you will need to write an advanced automation that handles the overwriting or meeting of the old data with the new data.
5. Airtable does not allow prefilled fields to be LOCKED, meaning that a user can always override a prefilled field (even if it’s hidden). If you need a prefilled field to be locked & hidden, then you can always use Fillout to hide and lock defaults.
6. You miss out on all the advanced features of Fillout’s forms.

So, instead of using prefilled links with Airtable’s forms, simply use Fillout’s advanced forms for Airtable because no prefilled links are required — you can simply update an existing Airtable record using a form.

Fillout is 100% free, and it also offers hundreds of other advanced features that Airtable’s native forms don’t offer, including the ability to create custom PDF files from a form submission, accept payments on forms, pre-fetch dynamic data from an Airtable record, customize the style and branding of your form, customize a theme for your form, display Airtable lookup fields on forms, create new linked records on a form, add a login page to your form, perform math or other live calculations on your forms, collect signatures on a form, create multi-page forms with conditional paths, connect a single form to dozens of external apps simultaneously, add CAPTCHAs to your form, and much more.

I show how to use a few of the advanced features of Fillout on these 2 Airtable podcast episodes:

• Using Fillout to update an existing Airtable record & create an eSignature approval process with PDF file creation.
• Using Fillout to create an order entry form with line items.

By the way, in those circumstances when you’re NOT trying to update an existing Airtable record but you STILL need to prefill a form, Fillout gives you 4 other ways to prefill a form — for a grand total of 5 different ways to prefill a form. And best of all, no prefilled links are required for 4 of these 5 methods.

Hope this helps!

If you’d like to hire the best Airtable consultant to help you with anything Airtable-related, please feel free to contact me through my website: Airtable consultant — ScottWorld

​@ScottWorld While the solution you listed is tricky, if the record only needs to be updated once can it be done? I want to avoid using any 3rd party extensions and update the existing record only using Airtable (prefill, linked records & forms). 

Airtable has a guide on how to do that here: https://support.airtable.com/docs/updating-records-using-a-form-in-airtable

Happy to help if you hit any issues setting it up!