> For AI agents: the complete documentation index is available at https://docs.flashnerd.com/llms.txt, the full documentation bundle is available at https://docs.flashnerd.com/llms-full.txt.

# FSRS parameters

Flashnerd's SRS scheduler uses **21 FSRS-6-compatible parameters**. They describe how the memory model updates after an answer. Most users can leave these at their built-in defaults and adjust [Desired Retention and learning steps](https://docs.flashnerd.com/reference/srs/scheduling.md) instead.

Open a set's **SRS Set Settings → Advanced Settings** to see **SRS Parameters (CSV)**. The grid numbers its cells **1–21**. Technical FSRS descriptions often number the same weights **w₀–w₂₀**, so cell 1 corresponds to w₀.

## What the groups control

| App cells | Model role                                                   |
| --------- | ------------------------------------------------------------ |
| 1–4       | Initial stability after each of the four answer grades.      |
| 5–8       | Initial difficulty and how difficulty changes after answers. |
| 9–11      | Stability growth after a successful longer-term recall.      |
| 12–15     | Stability after forgetting.                                  |
| 16–17     | Hard/Easy adjustments to successful-recall stability growth. |
| 18–20     | Short-term stability adjustments.                            |
| 21        | Forgetting-curve decay.                                      |

These weights work together. They are not independent user preferences such as “minutes before the next card.” For the underlying model, see the [FSRS algorithm documentation](https://github.com/open-spaced-repetition/awesome-fsrs/wiki/The-Algorithm).

## Enter a parameter set

Before changing parameters, keep a [collection backup](https://docs.flashnerd.com/guide/import-export/backups.md) and retain a copy of any custom values you may want to restore.

1. Open **Advanced Settings** for the intended set.
2. Enter individual values, or copy a compatible parameter list and tap **Paste** beside the parameter grid.
3. Check the cell positions and all highlighted validation errors.
4. Tap **Save Change**.

The header's Paste action accepts comma-, semicolon-, or whitespace-separated values and replaces the grid. It uses the first 21 tokens; missing trailing cells become blank. Pasting several values into an individual cell distributes them from that cell onward, leaving cells outside that pasted run unchanged.

**A blank cell uses the built-in default for that position.** An entirely blank grid uses all built-in defaults. A short list therefore mixes your entered values with defaults; do not assume a 17- or 19-value vector from a different FSRS version is a complete compatible set.

Nonempty values must be finite numbers within the permitted range for their position. Invalid values are marked in red and prevent saving. Pure text pasted through the header action produces a message instead of replacing the grid.

## Built-in values and accepted ranges

| Cell | Default | Accepted range |
| ---- | ------- | -------------- |
| 1    | 0.212   | 0.001–100      |
| 2    | 1.2931  | 0.001–100      |
| 3    | 2.3065  | 0.001–100      |
| 4    | 8.2956  | 0.001–100      |
| 5    | 6.4133  | 1–10           |
| 6    | 0.8334  | 0.001–4        |
| 7    | 3.0194  | 0.001–4        |
| 8    | 0.001   | 0.001–0.75     |
| 9    | 1.8722  | 0–4.5          |
| 10   | 0.1666  | 0–0.8          |
| 11   | 0.796   | 0.001–3.5      |
| 12   | 1.4835  | 0.001–5        |
| 13   | 0.0614  | 0.001–0.25     |
| 14   | 0.2629  | 0.001–0.9      |
| 15   | 1.6483  | 0–4            |
| 16   | 0.6014  | 0–1            |
| 17   | 1.8729  | 1–6            |
| 18   | 0.5425  | 0–2            |
| 19   | 0.0912  | 0–2            |
| 20   | 0.0658  | 0–0.8          |
| 21   | 0.1542  | 0.1–0.8        |

Use the values shown by your installed app if a later release changes the defaults.

## When changes take effect

Saving advanced settings **does not rewrite existing schedules or review logs**. The new parameters are used when a subsequent review session or queue rebuild constructs its scheduler. Start a new session to use the saved configuration consistently.

The current app provides manual parameter editing and pasting. It does not offer an automatic parameter-optimization or bulk-rescheduling workflow in this screen.

## Restore defaults

Choose **Reset to Default**, then **Save Change**. Empty cells showing their default hints are expected: the app does not need a manually filled copy of the default vector.