Every major SWD debug probe side by side — what they cost, how fast they are, what they support, and which one to pick for your use case.
What is SWD?Feature comparison across the most common debug probes for ARM Cortex-M development.
| J-Link BASE | J-Link PLUS | ST-Link V3 | DAPLink | CMSIS-DAP v2 | Black Magic Probe | |
|---|---|---|---|---|---|---|
| Price | €400 | €800 | €35 (STLINK-V3MINI) | Free (DIY) | $10-50 | €60 |
| USB speed | Full Speed | High Speed | High Speed | Full Speed | Varies | Full Speed |
| Max SWD clock | 15 MHz | 50 MHz | 24 MHz | ~10 MHz | Varies | ~4 MHz |
| Flash speed (typical) | ~1 MB/s | ~3 MB/s | ~1.5 MB/s | ~200 KB/s | Varies | ~200 KB/s |
| SWO trace | ✓ | ✓ | ✓ | ✗ | Some | ✗ |
| UART bridge (VCOM) | ✓ | ✓ | ✓ | ✓ | Some | ✓ |
| Cortex-M targets | All | All | STM32 only* | Most | Most | Many |
| Cortex-A/R | ✓ | ✓ | ✗ | ✗ | ✗ | ✗ |
| JTAG + SWD | ✓ | ✓ | ✓ | SWD only | Varies | ✓ |
| Open source firmware | ✗ | ✗ | ✗ | ✓ | ✓ | ✓ |
| GDB server | J-Link GDB Server | J-Link GDB Server | ST-Link GDB Server | pyOCD / OpenOCD | pyOCD / OpenOCD | Built-in |
| Commercial licence | Required for production | Required for production | Free (ST targets) | Free | Free | Free |
* ST-Link V3 works with non-ST targets through OpenOCD, but ST's own tools are STM32-only. Prices are approximate retail as of 2026.
The industry standard. Best flash speed, widest target support, excellent software (J-Link GDB Server, Ozone, J-Flash). The PLUS model with USB High Speed is significantly faster than the BASE.
Best for: Professional development, production programming, anyone willing to pay for the best tooling.
Drawbacks: Expensive. Licence restrictions — the EDU version can't be used commercially. The J-Link OB (on-board) on eval boards is locked to that board's chip vendor.
The STM32 companion. Ships on every ST Nucleo/Discovery board. The standalone STLINK-V3MINI is excellent value at ~€35. High Speed USB, decent flash speed, SWO trace, VCOM bridge.
Best for: Anyone working exclusively with STM32. The price and integration with STM32CubeIDE is hard to beat.
Drawbacks: ST's tooling only supports STM32 targets. Works with non-ST chips through OpenOCD but you lose the polished ST workflow. No official support for other Cortex-M vendors.
The open standard. ARM's spec for debug probes. Any MCU with USB can be a CMSIS-DAP probe — it's a firmware protocol, not a specific product. CMSIS-DAP v2 uses WinUSB (bulk transfers) for much better speed than v1 (HID).
Best for: DIY probes, projects that need an open and vendor-neutral probe interface, embedded in your own products as an on-board debug interface.
Drawbacks: Performance depends entirely on the hardware implementation. A cheap Full Speed USB implementation is slow. A High Speed USB implementation (like AT32F405-based probes) can match or exceed J-Link speeds.
ARM's reference debug probe firmware. Runs on NXP LPC/Kinetis MCUs. Originally for Mbed boards. Exposes the target as a USB mass storage device — drag-and-drop firmware flashing. Also supports CMSIS-DAP.
Best for: Educational boards, beginners who want drag-and-drop simplicity, Mbed ecosystem.
Drawbacks: Slow (Full Speed USB only). Limited target support compared to J-Link or CMSIS-DAP v2 implementations. The drag-and-drop flashing is convenient but not suitable for production.
GDB server on the probe itself. Unique approach — the probe runs a GDB server internally. Connect directly from GDB over USB CDC, no intermediate server software needed. Open source firmware.
Best for: GDB purists, minimalist setups, people who want a self-contained debug solution without running a server on the host.
Drawbacks: Slower than J-Link or ST-Link. Limited high-speed tracing. Smaller target device database than SEGGER or OpenOCD. Full Speed USB only.
An ST-Link V2 clone (~£3 on AliExpress) or the ST-Link built into any Nucleo board. It works, it's cheap, and there are a million tutorials. Use with OpenOCD or STM32CubeProgrammer.
J-Link PLUS if budget allows — the USB HS speed and SEGGER software quality are genuinely worth it for daily use. If you're STM32-only, the STLINK-V3MINI at €35 is exceptional value.
J-Link (with appropriate production licence) or the SEGGER Flasher series for standalone operation (no PC required). For high volume, the Flasher Compact or Flasher ARM are the industry defaults.
CMSIS-DAP v2 on a USB HS capable MCU. This is the direction the industry is heading — an open debug protocol that any hardware can implement, with pyOCD and probe-rs as the host-side software.
This is where existing options get expensive fast. A 7-probe J-Link setup costs €2,800-5,600+. Gang programmers (SEGGER Flasher, PEmicro) can flash in parallel but can't do functional testing, logic capture, or power measurement per target. Read more about multi-target testing →
This is the single biggest factor in real-world flash speed, and it's often overlooked.
Many popular probes — DAPLink, Black Magic Probe, most CMSIS-DAP v1 implementations, J-Link BASE, cheap ST-Link clones — are Full Speed only. The USB connection is the bottleneck, not the SWD protocol.
If you flash frequently or have large firmware images, a USB High Speed probe (J-Link PLUS, ST-Link V3, or a CMSIS-DAP v2 probe on a HS-capable MCU) makes a noticeable difference in your workflow.
We're building a 7-channel SWD test probe with per-channel logic analyser, UART capture, and current measurement. All over USB High Speed.
Multi-Target Testing Guide Register for Early Access