---
title: "validate()"
description: "sms.validate(input): SmsValidationResult fields, ValidationIssue codes, and what local validation cannot check."
---

## `sms.validate(input)`

Checks a message locally and estimates its segments. It is synchronous and free, and it never contacts a provider or claims that an account or sender is approved.

```ts
import { sms } from "./sms";

const check = sms.validate({ to: "+14155550123", body: "Your package is ready 📦" });

if (!check.supported) {
  for (const issue of check.issues) console.warn(issue.code, issue.field, issue.message);
}
console.log(check.encoding, check.segments, check.adapterCandidates);
```

Guide: [Validation and encoding](/sending/validation-and-encoding).

### Parameters

- `input: SmsSendInput`, the same input `send()` takes. See [send()](/reference/send#smssendinput).

### Returns: `SmsValidationResult`

`SegmentPreview` plus four fields:

| Field | Type | Meaning |
| --- | --- | --- |
| `supported` | `boolean` | `true` when the primary adapter can send the message and the message has no issues. |
| `issues` | `readonly ValidationIssue[]` | Every problem found, across the message and every adapter. |
| `adapterCandidates` | `readonly string[]` | Adapters that could send it, in configured order. Empty when the message itself is invalid. |
| `providerOptionsFor` | `readonly string[]` | The candidates in `adapterCandidates` that have an entry in `providerOptions`, in configured order. Each of these sends its own entry if it ends up sending. Empty when the message itself is invalid or no candidate has an entry. |
| `encoding` | `"gsm7" \| "ucs2"` | |
| `segments` | `number` | Estimated segments, `0` for an empty body. |
| `units` | `number` | Septets (GSM-7) or UTF-16 code units (UCS-2). |
| `unitsPerSegment` | `number` | 160 or 153 (GSM-7), 70 or 67 (UCS-2). |
| `remainingInSegment` | `number` | Units left before another segment starts. |
| `containsUnicode` | `boolean` | At least one character forces UCS-2. |
| `nonGsmCharacters` | `readonly string[]` | Distinct characters that forced UCS-2. |

`supported` matches what `send()` does before any request. When the primary adapter makes `supported` false, `send()` throws even with fallback on.

Message-level issues come first: recipient, body, field formats, and `providerOptions` checked against every configured adapter. When there are any, adapters are not checked, and `adapterCandidates` and `providerOptionsFor` are empty.

## `ValidationIssue`

```ts ignore="type listing"
type ValidationIssue = {
  readonly code: ValidationIssueCode;
  readonly field: ValidationField;
  readonly message: string;
  readonly provider?: string; // set when the issue applies to one adapter
};
```

| `code` | `send()` throws | Meaning |
| --- | --- | --- |
| `invalid_recipient` | `InvalidRecipientError` | `to` is not E.164. |
| `invalid_sender` | `InvalidSenderError` | The sender is malformed, such as a sender ID over 11 characters, a short code that is not 3 to 8 digits, a Twilio Messaging Service SID that is not `MG` plus 32 hex, or a Telnyx alphanumeric sender without `messagingProfileId`. |
| `missing_sender` | `InvalidSenderError` | No `from` and no adapter default. |
| `empty_body` | `InvalidMessageError` | Empty body without media, or any empty body on Vonage. |
| `unsupported_field` | `UnsupportedFieldError` | The adapter cannot send this field or sender type, Twilio `sendAt` without a Messaging Service sender, or a `providerOptions` key the adapter does not accept or that names a parameter the SDK sets. |
| `invalid_field` | `InvalidMessageError` | A malformed field, a value outside the adapter's range, or a `providerOptions` value of the wrong type. |

`ValidationField` is `"to" | "from" | "body" | "mediaUrls" | "sendAt" | "validityPeriodSec" | "webhookUrl" | "idempotencyKey" | "providerOptions"`.

## What it does not check

- Whether the sender is provisioned or registered in your account.
- Whether the destination accepts your sender type or MMS.
- Recipient opt-outs held by the provider, account balance, or permissions.

The provider reports these as rejections at send time.

## Types

`SmsValidationResult`, `ValidationIssue`, `ValidationIssueCode`, `ValidationField`, and `SegmentPreview` are exported as types from `@opencoredev/sms-sdk`.