> For the complete documentation index, see [llms.txt](https://docs.mtoolstec.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.mtoolstec.com/hardware/rfid-nfc-and-uhf-hardware/proxmark3-x/lf-and-hf.md).

# LF and HF Operations

Commands in this page run at the Proxmark3 client prompt, after connecting the device. Keep the client and firmware versions matched.

## First Identification

Place one tag over the appropriate antenna:

```
lf search
```

For a high-frequency tag:

```
hf search
hf 14a reader
```

`hf 14a reader` is an ISO14443A identification command. Use the matching protocol group for other tag families. Tag discovery does not imply access to protected memory.

## Command Groups

| Group       | Use                                  |
| ----------- | ------------------------------------ |
| `lf`        | LF protocol tools and discovery      |
| `lf t55xx`  | T55xx configuration and memory tools |
| `hf 14a`    | ISO14443A                            |
| `hf 14b`    | ISO14443B                            |
| `hf 15`     | ISO15693                             |
| `hf mf`     | MIFARE Classic                       |
| `hf mfu`    | MIFARE Ultralight                    |
| `hf felica` | FeliCa                               |

Run `help` or the group name to inspect the installed command tree. Use a command's `-h` help before providing arguments: historical product documentation may use syntax from older client revisions.

## Independent LF Mode

Mode 2 provides the product's independent 125 kHz LF read/write workflow. Read the source using LF Read, replace it with a compatible writable destination, and use LF Write. Confirm the result by reading it again.

This mode does not replace the interactive client's protocol tools and does not establish support for every LF format or 134 kHz tag.

## T55xx Diagnostics

Start with identification and readback:

```
lf t55xx detect
lf t55xx read -h
lf t55xx write -h
```

Block 0 controls the tag's modulation and bitrate. Record the detected configuration before editing it. A wrong configuration can make later discovery fail even when the chip is still writable. Use the installed client's exact argument syntax; do not copy old `wr b 0 d ...` forms without checking help.

The [T55xx troubleshooting guide](https://proxmark3x.mtoolstec.com/commands/low-frequency/troubleshooting-writing-to-t55xx-cards-with-proxmark3) provides additional context. A wipe is a destructive reset, not a required diagnostic step.

## Antenna and Connection Checks

If tags are not detected, confirm the mode, antenna position, antenna-board connection, and client / firmware compatibility. Use `hw tune` for diagnostics when supported by the build. A protocol command appearing in help does not guarantee that this hardware revision supports its required RF frequency or accessories.