Labels override

Every string the renderer shows — buttons, validation messages, calendar labels, upload notices — can be overridden per embed via the labels attribute, which takes a JSON object:

<forms-engine
  public-id="q_a1b2c3d4e5"
  api-base="https://forms.your-domain.com"
  labels='{"finish":"Enviar","requiredError":"Este campo es obligatorio."}'>
</forms-engine>

This is a strings override, not internationalization: question prompts, options, and section titles come from the questionnaire itself and are single-language per questionnaire — the override localizes the renderer’s chrome around them.

How merging works:

Keys you supply replace the built-in English; every key you don’t supply keeps its English default — partial overrides are fine.
Unknown keys and non-string values are ignored silently.
Unparseable JSON logs a console warning and falls back to all defaults — a typo can’t blank the UI.
Some strings interpolate parameters in {braces} — keep the placeholder in your replacement (e.g. "textMaxLengthError": "Máximo {max} caracteres.").

Key	Default
`next`	Next
`back`	Back
`finish`	Finish
`finishing`	Submitting…
`loading`	Loading…
`loadErrorTitle`	Something went wrong
`loadErrorNotFound`	This questionnaire is not available.
`loadErrorGeneric`	The questionnaire could not be loaded.
`emptyState`	There is nothing to fill in right now.
`completionTitle`	Thank you!
`completionMessage`	Your response has been submitted.
`savingError`	Your answers aren’t saving right now. We’ll keep trying — please don’t close this page.
`requiredError`	This question is required.
`unknownTypePlaceholder`	This question requires a newer version of the form component.
`alreadySubmittedMessage`	You’ve already submitted this form.
`refMissingError`	This form is misconfigured: an external reference is required.
`attentionOne`	1 question needs attention before continuing.
`attentionMany`	{n} questions need attention before continuing.
`stepsNavLabel`	Steps
`tabsNavLabel`	Sections of this step

Answer validation

Key	Default
`textMaxLengthError`	Please use at most {max} characters.
`formatErrorEmail`	Enter a valid email address.
`formatErrorPhone`	Enter a valid phone number.
`formatErrorDate`	Enter a valid date (YYYY-MM-DD).
`dateMinError`	The date must be on or after {min}.
`dateMaxError`	The date must be on or before {max}.
`datePastError`	The date cannot be in the past.
`dateFutureError`	The date cannot be in the future.
`numberInvalidError`	Enter a number.
`numberMinError`	The value must be at least {min}.
`numberMaxError`	The value must be at most {max}.
`numberWholeError`	Enter a whole number.
`numberDecimalsError`	Use at most {n} decimal places.
`addressInvalidError`	Enter an address.
`zipFormatError`	Enter a valid ZIP code (12345 or 12345-6789).
`uploadInvalidError`	Upload a file.

Choice controls

Key	Default
`checkboxMaxHint`	Select up to {n}.
`dropdownPlaceholder`	Select…
`dropdownSearchLabel`	Search options
`dropdownSearchPlaceholder`	Type to filter…
`dropdownNoMatches`	No matches
`dropdownClearLabel`	Clear selection

Date input & calendar

Key	Default
`datePlaceholder`	YYYY-MM-DD
`dateOpenCalendarLabel`	Open calendar
`dateDialogLabel`	Choose a date
`datePrevMonthLabel`	Previous month
`dateNextMonthLabel`	Next month
`dateMonthNames`	January,February,…,December — comma-separated, January first
`dateWeekdayNames`	Su,Mo,Tu,We,Th,Fr,Sa — comma-separated, Sunday first

Address

Key	Default
`addressCountry`	Country
`addressLine1`	Street address
`addressLine2`	Address line 2
`addressCity`	City
`addressState`	State / Province / Region
`addressStateUs`	State
`addressPostalCode`	Postal code
`addressZipCode`	ZIP code
`addressCountryPlaceholder`	Select a country…
`addressStatePlaceholder`	Select a state…
`addressCountrySearchLabel`	Search countries
`addressStateSearchLabel`	Search states

File upload

Key	Default
`uploadPrompt`	Drag & drop or click to browse
`uploadLimitReached`	File limit reached
`uploadSingleAttached`	A file is already attached — remove it first.
`uploadMaxFilesNotice`	Up to {n} files are allowed.
`uploadSurplusNotice`	Only {n} more can be added — the rest were skipped.
`uploadTypeNotAccepted`	This file type isn’t accepted. Allowed: {extensions}.
`uploadTooLarge`	This file is larger than the {max} MB limit.
`uploadFailed`	The upload failed.
`uploadRetry`	Retry
`uploadWaitToContinue`	Waiting for the upload to finish.
`uploadRemoveLabel`	Remove {name}
`uploadCancelLabel`	Cancel uploading {name}
`uploadDismissLabel`	Dismiss {name}
`uploadUploadingLabel`	Uploading {name}
`uploadPreviewTag`	preview — not uploaded
`uploadSummaryNoTypes`	No file types configured
`uploadSummaryOneFile`	1 file
`uploadSummaryManyFiles`	up to {n} files
`uploadSummaryEach`	{n} MB each

That’s the complete catalog — 74 keys. If a string appears in the UI that no key covers, that’s a bug worth reporting.

One wrapper note: the React and Angular wrappers don’t expose a labels prop — to use overrides there, use the web component directly (both wrappers are thin layers over it). See React and Angular.