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67 lines
3.4 KiB
Markdown
67 lines
3.4 KiB
Markdown
NIP-54
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======
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Inline Resource Metadata
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------------------------
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`draft` `optional` `author:arthurfranca` `author:Giszmo` `author:jb55` `author:vitorpamplona`
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Inline resource metadata is additional information associated with urls in notes that clients can optionally use to enhance resource loading.
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It uses [URI Fragment](https://en.wikipedia.org/wiki/URI_fragment) that agents (such as web browsers) never send to the server. Because of this, the url is fetched **without** the fragment parameters, unlike using query parameters.
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The URI fragment follows [media fragments structure](https://www.w3.org/TR/media-frags/#general-structure). For example, one could use `t=number_of_seconds` to start playing a video at the specified position along with an extra [percent-encoded](https://www.ietf.org/rfc/rfc3986.txt) name-value pair separated by `&` char like `https://xyz.com/a-video.mp4#t=24&a%20name=a%20value`. **Notice the usage of `#` instead of `?`.**
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The metadata can be appended to any url, like this [NIP-21](21.md) one: `nostr:nevent1qq...pm#a-metadata-name=a-metadata-value`.
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One may also add `url` tags to events to aid in loading resource placeholders on clients that postpone or don't do event `.content` parsing.
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## NIP-94 File Fragments
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Besides available w3c and proprietary URI fragment usage, nostr uses existing [NIP-94](94.md) tags as file fragment name-value pairs. NIP-94 event `.content` is equivalent to `alt` fragment field. For example, one could join the following strings to form an image url with inline metadata:
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- `https://nostr.build/i/863321bb1ae68830ebcf9a343ca0a5e0ce2323d0a55b7fbe86f7a886cf61db8d.jpg`
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- `#`
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- `m=image%2Fjpeg`
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- `&`
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- `dim=3024x4032`
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- `&`
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- `alt=A%20scenic%20photo%20overlooking%20the%20coast%20of%20Costa%20Rica`
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- `&`
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- `blurhash=eVF%24%5EOI%3A%24%7BM%7Bo%23*0-nNFxakD-%3FxVM%7DWEWB%25iNKxvR-oetmo%23R-aen%24`
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Multiple array values use repeated names and are positioned in the same order of ocurrence in the tag array. For instance, `["aes-256-gcm", 'i-am-a-key', 'i-am-an-iv']` becomes `aes-256-gcm=i-am-a-key&aes-256-gcm=i-am-an-iv`.
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### Event Example:
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```js
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{
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"kind": 1,
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"content": "What a great place! https://xyz.com/example.jpg#m=image%2Fjpeg&dim=3024x4032&alt=A%20scenic%20photo%20overlooking%20the%20coast%20of%20Costa%20Rica&blurhash=eVF%24%5EOI%3A%24%7BM%7Bo%23*0-nNFxakD-%3FxVM%7DWEWB%25iNKxvR-oetmo%23R-aen%24`",
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// ... other event fields
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}
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```
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## Tag Usage
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Some event kinds may have been designed with urls inside tags instead of in `.content`. For these cases, use `url` tags (or `r` tags if it needs to be indexed by relays – in this case, metadata fragment keys and query parameter keys SHOULD be arranged in ascending order).
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### Tag Examples:
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A kind 30023 event JSON file (with `nostr/30023` MIME type):
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`["url", "https://xyz.com/example.json#m=nostr%2F30023"]`
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A PDF file without extension with added MIME type information:
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`["r", "https://xyz.com/article02#m=application%2Fpdf"]`
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## Recommended client behavior
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When uploading images during a new post, clients can collect metadata
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after the image is uploaded and then include the url with inline metadata in the post.
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When pasting urls during post composition, the client could download the image
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and add some metadata before the post is sent.
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Clients can use `alt` value to add accessible text for people who prefer not to
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load images, visibility-impaired users, or text clients.
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