---
title: Jitter
description: Randomize exponentialBackoff/linearBackoff delays to avoid synchronized retries against a shared upstream.
type: package
package: "@zap-studio/retry"
---

When many clients fail at the same time and retry on the same deterministic schedule, they hammer the upstream in synchronized waves. `jitter` randomizes the computed delay so retries spread out instead.

`exponentialBackoff(...)` and `linearBackoff(...)` accept an optional `jitter` option, applied to the delay after it's capped at `maxDelayMs`.

```ts
import { exponentialBackoff } from "@zap-studio/retry";

const policy = exponentialBackoff({
  maxAttempts: 5,
  baseDelayMs: 100,
  maxDelayMs: 2_000,
  jitter: "full",
});
```

## Modes

| Mode      | Formula                                | Description                                                          |
| --------- | -------------------------------------- | -------------------------------------------------------------------- |
| `"full"`  | `random(0, delayMs)`                   | Maximum spread; strongest protection against synchronized retries.   |
| `"equal"` | `delayMs / 2 + random(0, delayMs / 2)` | Keeps a floor at half the computed delay; less spread than `"full"`. |

With a capped delay of `1_000` ms, `"full"` produces any value in `[0, 1_000]`; `"equal"` produces any value in `[500, 1_000]`.

## Custom Random Source

Pass `{ mode, random }` instead of the mode shorthand to override the random source — useful for deterministic tests:

```ts
const policy = exponentialBackoff({
  maxAttempts: 5,
  baseDelayMs: 100,
  maxDelayMs: 2_000,
  jitter: { mode: "full", random: () => 0.5 },
});
```

`random` must return a number in `[0, 1)`. Defaults to `Math.random`.

## Standalone Use

`applyJitter(delayMs, jitter?)` is also exported directly, for custom policies:

```ts
import { applyJitter } from "@zap-studio/retry";

const delayMs = applyJitter(1_000, "equal");
```

## See Also

- [exponentialBackoff](/retry/exponential-backoff)
- [linearBackoff](/retry/linear-backoff)
- [Custom Policies](/retry/custom-policies)