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69 lines
3.3 KiB
Markdown
69 lines
3.3 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.
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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`.
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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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It is suggested to also add `imeta` tags to events to aid in loading resource placeholders.
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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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- `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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## imeta tag
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Metadata fragments are great for sharing urls with extra embedded metadata. They are also good for copying and pasting a resource's url from one note to a new one without losing its metadata.
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But some clients can prepare image and video placeholders faster if specific fields are present outside of `.content`.
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For these resources, it is suggested to also add `dim`, `alt` and `blurhash` (e.g. of a specific video frame), if available, to `imeta` tags.
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### Complete 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#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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"tags": [
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[
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"imeta",
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"url https://xyz.com/example.jpg",
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"dim 3024x4032",
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"alt A scenic photo overlooking the coast of Costa Rica",
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"blurhash eVF$^OI:${M{o#*0-nNFxakD-?xVM}WEWB%iNKxvR-oetmo#R-aen$"
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]
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]
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// ... other event fields
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}
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```
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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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