# How to Read a .lottie File
Choose between DotLottie and DotLottieReader to load or inspect an existing .lottie file, depending on your memory and mutation needs.

# How to Read a .lottie File

There are two ways to read a `.lottie` file, and which one you want depends on whether you need to modify it and how large it is.

## Option 1: Full load with `DotLottie`

Use this when you plan to **modify** the package after reading it, or when the file is small enough that loading everything into memory doesn't matter.

```javascript
const { DotLottie } = require("@lottiefiles/dotlottie-io");

const dl = DotLottie.fromFile("package.lottie");
// or: DotLottie.fromBytes(readFileSync('package.lottie'))

dl.animationIds();
dl.getAnimationJson("hero");
```

Every entry is parsed on load, so subsequent reads and any mutations (`addAnimation`, `removeTheme`, etc.) are immediate.

## Option 2: Lazy access with `DotLottieReader`

Use this when you only need a **handful of specific entries** out of a large archive, or you want to minimize memory use.

```javascript
const { DotLottieReader } = require("@lottiefiles/dotlottie-io");

// Holds a live file handle — nothing but the manifest is read up front
const reader = DotLottieReader.open("large-library.lottie");

console.log(reader.animationIds()); // from the manifest, free
const heroJson = reader.getAnimationJson("hero"); // reads exactly one ZIP entry
```

`DotLottieReader.open()` keeps the file handle open and seeks directly to each requested entry — the rest of the archive is never read into memory. This is Node.js-only (there's no filesystem in WASM); in the browser, use `fromBytes`:

```javascript
const reader = DotLottieReader.fromBytes(uint8ArrayOfFileContents);
const font = reader.getFont("MyFont.ttf"); // Buffer | null
```

`DotLottieReader` is **read-only** — there's no method to mutate through it or promote it to a `DotLottie` in place. If you decide partway through that you need to mutate what you've loaded, load the same source again with `DotLottie.fromFile`/`fromBytes` instead.

## Which to use

| Situation                                           | Use               |
| --------------------------------------------------- | ----------------- |
| You'll modify the package after reading             | `DotLottie`       |
| The file is small, or you need most of its contents | `DotLottie`       |
| You need one or two entries from a large archive    | `DotLottieReader` |
| You're auditing many files in a batch job           | `DotLottieReader` |

## Related

- [Architecture](/docs/tools/dotlottie-io/core-concepts/architecture)
- [`DotLottie` API reference](/docs/tools/dotlottie-io/api/dotlottie-class)
- [`DotLottieReader` API reference](/docs/tools/dotlottie-io/api/dotlottie-reader-class)