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# Function: importX509
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â–¸ **importX509**(`x509`, `alg`, `options?`): `Promise`<[`KeyLike`](../types/types.KeyLike.md)\>
Imports the SPKI from an X.509 string certificate as a runtime-specific public key representation
(KeyObject or CryptoKey). See [Algorithm Key
Requirements](https://github.com/panva/jose/issues/210) to learn about key to algorithm
requirements and mapping.
**`example`** Usage
```js
const algorithm = 'ES256'
const x509 = `-----BEGIN CERTIFICATE-----
MIIBXjCCAQSgAwIBAgIGAXvykuMKMAoGCCqGSM49BAMCMDYxNDAyBgNVBAMMK3Np
QXBNOXpBdk1VaXhXVWVGaGtjZXg1NjJRRzFyQUhXaV96UlFQTVpQaG8wHhcNMjEw
OTE3MDcwNTE3WhcNMjIwNzE0MDcwNTE3WjA2MTQwMgYDVQQDDCtzaUFwTTl6QXZN
VWl4V1VlRmhrY2V4NTYyUUcxckFIV2lfelJRUE1aUGhvMFkwEwYHKoZIzj0CAQYI
KoZIzj0DAQcDQgAE8PbPvCv5D5xBFHEZlBp/q5OEUymq7RIgWIi7tkl9aGSpYE35
UH+kBKDnphJO3odpPZ5gvgKs2nwRWcrDnUjYLDAKBggqhkjOPQQDAgNIADBFAiEA
1yyMTRe66MhEXID9+uVub7woMkNYd0LhSHwKSPMUUTkCIFQGsfm1ecXOpeGOufAh
v+A1QWZMuTWqYt+uh/YSRNDn
-----END CERTIFICATE-----`
const ecPublicKey = await jose.importX509(x509, algorithm)
```
#### Parameters
| Name | Type | Description |
| :------ | :------ | :------ |
| `x509` | `string` | - |
| `alg` | `string` | JSON Web Algorithm identifier to be used with the imported key. |
| `options?` | [`PEMImportOptions`](../interfaces/key_import.PEMImportOptions.md) | - |
#### Returns
`Promise`<[`KeyLike`](../types/types.KeyLike.md)\>
|
