> For the complete documentation index, see [llms.txt](https://codifi-fdm.gitbook.io/codifi-docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://codifi-fdm.gitbook.io/codifi-docs/web-app/map-setup-and-offline-areas/offline-areas.md).

# Offline Areas

**Offline Areas** are pre-downloaded chunks of map tiles — both the basemap and any [Map Overlays](/codifi-docs/web-app/map-setup-and-offline-areas/map-overlays.md) you've added — that mobile devices keep locally so the map keeps working when the network drops.

Field crews work offline more often than they realize. Backcountry sites, remote roads, dense buildings, basements, and dead zones all break web connectivity, but field work doesn't stop. Setting up Offline Areas before crews go out means the map keeps showing context — overlays, basemap, satellite imagery — regardless of signal.

{% hint style="warning" %}
**If you skip Offline Areas, the map turns into a blank gray grid the moment a crew loses signal.** They can still capture Records (Codifi syncs Records when connectivity returns), but they won't see their context. Set Offline Areas before crews go out, not after.
{% endhint %}

***

## How to Add an Offline Area

1. Open your Project, then from the left navigation menu choose **Map Setup** → **Offline Areas**.
2. Click **+ Offline Area**.
3. Pan and zoom the map to the region your crew will work in. The area should fall inside your [Project Map Extent](/codifi-docs/web-app/map-setup-and-offline-areas/project-map-extent.md) — set the extent first if you haven't.
4. Use the **Draw** tool to outline the offline coverage area as a rectangle or polygon.
5. Pick a **maximum zoom level**. Deeper zoom = more detail but a larger download. **Zoom 19** is a sane default for field work; zoom 21–22 is overkill for most Projects.
6. Give the area a clear name, e.g. *"Camp County — Pittsburg city center"* or *"Survey Block A — west half"*.
7. **Save**.

Codifi schedules the tile download. The size estimate appears next to the area; once the download completes on the server side, the area is ready to push to mobile.

***

## When Field Crews Sync

When a crew opens the Project on their iPad and **pulls down to sync** — or runs an explicit sync from the Project menu — the offline area downloads automatically. After that, the map in that area works regardless of connectivity.

We recommend crews complete this sync **on Wi-Fi the night before fieldwork**, not in the field on cellular. Offline area downloads can be hundreds of megabytes; downloading them over a weak signal at the trailhead is a bad start to the day.

***

## Sizing Guidance

| Area    | Approx. download size at zoom 19 |
| ------- | -------------------------------- |
| 1 km²   | 30–80 MB                         |
| 10 km²  | 300 MB – 1 GB                    |
| 100 km² | 1–3 GB                           |

Sizes vary with basemap detail (urban areas are bigger than open desert) and the number/complexity of overlays attached.

{% hint style="info" %}
**Split big areas into smaller ones.** If you're covering a large Project, create multiple smaller Offline Areas instead of one giant one. Crews can pick which areas they need on a given day, and an unfinished download in one area doesn't block the others. It also makes it easier to free up device storage by removing finished areas.
{% endhint %}

***

## Maximum Zoom in Plain Terms

A higher max zoom means crews can pinch in further before the map goes blurry. Pick based on what your team needs:

| Max zoom | What it's good for                                                            |
| -------- | ----------------------------------------------------------------------------- |
| 16       | High-altitude overview, large reconnaissance areas                            |
| 18       | Most surveys — buildings and roads are clearly visible                        |
| **19**   | **Default for fieldwork** — building details, vegetation, individual features |
| 20–21    | Highly detailed pedestrian survey, small features                             |
| 22       | Maximum tile detail. Rarely needed; downloads bloat fast                      |

Higher zoom roughly **quadruples** the tile count for each level you add. Zoom 21 is roughly 16× the tiles of zoom 19. Choose the lowest zoom level that supports your work.

***

## Updating an Offline Area

If you resize an offline area, change its max zoom, or add overlays after the initial download, the area's tile set is now out of date.

* On the **web**, save the change. Codifi schedules a refresh of the tile set.
* On **mobile**, each device needs to **re-sync the Project** to pick up the new tiles. Pull down on the Project screen, or run an explicit sync from the Project menu.

Until the device re-syncs, it will use the previously downloaded tiles — older overlays may not show.

***

## Removing an Offline Area

Removing an Offline Area on the web frees up the corresponding storage on every device that previously downloaded it (after the next sync). Use this to clean up after a Project area shrinks, after a Project closes, or to make room on a device for a new area.

***

## See Also

* [Project Map Extent](/codifi-docs/web-app/map-setup-and-offline-areas/project-map-extent.md) — frame the Project area first
* [Map Overlays](/codifi-docs/web-app/map-setup-and-offline-areas/map-overlays.md) — overlays bundle into Offline Area downloads automatically