# Filters

### Filter System Concepts

Several Kanban API types operate on the board's filter system. Before using them, it helps to understand the two distinct filter layers:

**Filter Panel** — the visible filter state. Users can see, edit, and apply these conditions through the Filter Side Panel. Changes to the Filter Panel do not affect the board until the user clicks Apply, or until an **Apply Filter Conditions** handler fires.

**Hidden conditions** — filter conditions that are not visible in the Filter Panel. They still affect which records are shown on the board. Because users cannot see them, always provide a way for users to clear hidden conditions when you use them.

These two layers are independent. Actions that clear the Filter Panel do not touch hidden conditions, and vice versa.

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### Filter Action Quick Reference

| Action                            | Target                | Auto-applies              | Replaces or merges     |
| --------------------------------- | --------------------- | ------------------------- | ---------------------- |
| Apply Filters Template            | Filter Panel          | ✅ Yes                     | Replaces all           |
| Apply Filters Template Conditions | Hidden conditions     | ✅ Yes                     | Merges                 |
| Select Filters Template           | Filter Panel          | ❌ No                      | Replaces all           |
| Merge Filters Template            | Filter Panel          | ❌ No                      | Merges                 |
| Add Filter Condition              | Filter Panel          | ❌ No                      | Always appends         |
| Add Labels Filter Condition       | Filter Panel          | ❌ No                      | Adds (deduplicates)    |
| Apply Filter Conditions           | Filter Panel + Hidden | ✅ Yes — this is the apply | —                      |
| Clear Filter Conditions           | Filter Panel          | ❌ No — chain Apply        | Clears all             |
| Reset Filter Conditions           | Filter Panel          | ❌ No — chain Apply        | Restores View defaults |
| Clear Hidden Conditions           | Hidden conditions     | ❌ No — chain Apply        | Clears all             |