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Update large-assets.md #130

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Update large-assets.md
CaptainInler Mar 30, 2026
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typo corrected
CaptainInler Mar 30, 2026
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14 changes: 8 additions & 6 deletions download-data/stac-api/large-assets.md
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Expand Up @@ -4,19 +4,21 @@ Assets larger than **50 GB** cannot be downloaded with a regular HTTP `GET` or `

The workaround is to use **HTTP range requests**, which bypass the CloudFront limit by fetching the file in sequential chunks directly from the S3 origin.

## How It Works
The actual download is completed in this steps:
1. Probe the asset
2. Download the file in chunks
3. Optional: Verify SHA‑256 checksum

A `GET` request with the header `Range: bytes=0-0` is sent first to probe the asset.
## Probe the asset
Send a `GET` request with the header `Range: bytes=0-0` to probe the asset.
The S3 origin responds with `HTTP 206 Partial Content` and includes two useful headers:

| Header | Value |
| ------------------- | ----------------------------------------------------------------- |
| `Content-Range` | `bytes 0-0/<total_size>` — the total size of the object |
| `x-amz-meta-sha256` | SHA-256 hex digest of the full object (when set by the publisher) |

The file is then downloaded chunk by chunk using `Range: bytes=<start>-<end>`, and the final file is verified against the expected size and checksum.

You can probe an asset manually with `curl`:
Example to probe an asset manually with `curl` on Linux:

```bash
curl --silent --show-error --location \
Expand All @@ -39,7 +41,7 @@ x-amz-meta-sha256: <hex>
`HEAD` requests are **also blocked** by CloudFront for objects > 50 GB. Always use `GET` with a `Range` header to probe asset metadata.
:::

## Download Script
## Download

The script below requires **Python 3.6+ and no third-party packages** (stdlib only). It works on Linux, macOS, and Windows.

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