> Documentation index: https://gethologram.ai/llms.txt

# Verification

> The one rule that makes a download from anywhere safe, and the three ways to apply it.

A file you downloaded is only as trustworthy as the host that served it, unless you already knew what its bytes should hash to. The hub gives you that number before you fetch anything.

## The rule

Hash what arrives. Keep the file only if its SHA-256 equals the value the index gave you. The expected hash comes from the index and never from the source that served the bytes.

The hub does not verify on read. It cannot: the bytes never pass through it. Verification happens on your machine, or inside a client that does it for you.

## Where the expected hash comes from

| Dialect | Field | Source of truth |
| --- | --- | --- |
| Hugging Face Hub API | `oid` in `/api/models/<owner>/<name>/tree/main` | the index |
| `SHA256SUMS` | one line per file, in `sha256sum` format | generated by the hub from the index; never redirected |
| OCI | each layer's `digest` in the manifest | the index; a layer is one raw file, so its digest is the file's SHA-256 |
| Ollama | the layer digests Ollama checks itself | the index |
| Objects | `files[].sha256` in the model object | the object, whose own address is the BLAKE3 of its bytes |

The `Etag` on a `/resolve/` redirect is the same SHA-256, quoted. It is a convenience, not a second source: it is copied from the index.

## Check one file

```bash
curl -sL https://gethologram.ai/hexgrad/Kokoro-82M/resolve/main/EVAL.md -o EVAL.md
echo "9b4d7a54809bf22127d19d936d9e749249e1a655e2e0a1df8a6546f77a819658  EVAL.md" | sha256sum -c
```

```
EVAL.md: OK
```

## Check a whole download

Inside the model directory, with no tool of the hub's:

```bash
curl -s https://gethologram.ai/hexgrad/Kokoro-82M/resolve/main/SHA256SUMS | sha256sum -c
```

```
.gitattributes: OK
DONATE.md: OK
EVAL.md: OK
…
```

`sha256sum -c` exits non-zero if any file fails or is missing, so this works as a gate in a script. For a partial download, add `--ignore-missing` so only the files you have are checked:

```bash
curl -s https://gethologram.ai/hexgrad/Kokoro-82M/resolve/main/SHA256SUMS | sha256sum -c --ignore-missing
```

## Clients that check for you

| Client | What it checks | What you do |
| --- | --- | --- |
| Ollama | the SHA-256 of every layer, before the model is usable | nothing |
| oras, modctl, skopeo, crane, containerd | every blob against its digest | nothing |
| `huggingface_hub` | the size it was told to expect; not the hash | run `SHA256SUMS` in the snapshot directory |
| `curl` | nothing | `sha256sum -c` |

## On a mismatch

Drop the file and fetch it again from another source: put `/via/ipfs` or `/via/modelscope` in front of the path. The expected hash does not change; only the source does. If every source disagrees with the index, the index is wrong for that file, and the hub wants to know: use `POST /api/account/request` from a signed-in account, or open an issue on the [repository](https://github.com/Hologram-Technologies/hologram-live).

## Check an object

Objects are addressed by BLAKE3, not SHA-256. The address you asked for must equal the BLAKE3 of the bytes you received. With the `blake3` Python package:

```bash
curl -s https://gethologram.ai/api/v1/objects/blake3:3cc11e52049117dfc397240fddc7a4d3aa392ded7f623986e4e5757371363d9e -o model.json
python3 -c "from blake3 import blake3; print(blake3(open('model.json','rb').read()).hexdigest())"
```

```
3cc11e52049117dfc397240fddc7a4d3aa392ded7f623986e4e5757371363d9e
```

The [Objects](https://gethologram.ai/docs/objects.md) page explains what that object is.