diff --git a/Guide.md b/Guide.md
new file mode 100644
index 0000000..29cf1cd
--- /dev/null
+++ b/Guide.md
@@ -0,0 +1,202 @@
+# wg-mtu-auto — Practical Guide
+
+This guide shows **how to *determine* and *set*** correct MTU values:
+
+* **with WireGuard** (`wg0`), and
+* **without WireGuard** (just your egress interface like `eth0`/`wlan0`).
+
+The tool can:
+
+* auto-detect your **egress interface**
+* optionally **probe Path MTU (PMTU)** to one or more remote targets
+* compute a safe **WireGuard MTU** (`effective_mtu - 80` by default)
+* **apply** MTU to `wg0` and/or your egress interface
+
+---
+
+## TL;DR recipes
+
+### 1) Just compute & set WireGuard MTU (no PMTU probing)
+
+```bash
+sudo automtu
+# Equivalent from repo:
+# sudo python3 main.py
+```
+
+* Detects egress (e.g., `eth0`), reads its MTU (e.g., 1500)
+* Computes `wg0` MTU = `egress_mtu - 80` (min clamp 1280)
+* Applies to `wg0` (if present)
+
+Dry-run:
+
+```bash
+automtu --dry-run
+```
+
+---
+
+### 2) Compute & apply MTU on *egress* (non-WireGuard)
+
+Useful if you want the *link itself* (e.g., `eth0`) to use the discovered PMTU.
+
+```bash
+sudo automtu --pmtu-target 1.1.1.1 --apply-egress-mtu
+```
+
+* Probes PMTU to `1.1.1.1`, applies that result to `eth0`
+* Also computes a matching WireGuard MTU (`PMTU - 80`) and sets `wg0` (if present)
+
+> If the selected egress is `wg0`, egress application is **skipped** on purpose.
+
+---
+
+### 3) With WireGuard peers: auto-add endpoints as PMTU targets
+
+```bash
+sudo automtu --auto-pmtu-from-wg
+```
+
+* Reads `wg0` peer endpoints (`wg show ...` / `wg showconf`)
+* Probes PMTU to those endpoints
+* Picks an **effective PMTU** (policy = `min` by default)
+* Applies **`wg0` MTU = effective PMTU − 80**
+
+Add extra targets & choose different policy:
+
+```bash
+sudo automtu --auto-pmtu-from-wg \
+  --pmtu-target 46.4.224.77,1.1.1.1 \
+  --pmtu-policy median
+```
+
+---
+
+### 4) Force a specific WireGuard MTU (override)
+
+```bash
+sudo automtu --set-wg-mtu 1372
+```
+
+* Skips the computed value and **forces** 1372 on `wg0` (clamped to ≥1280)
+
+---
+
+## When to use which approach?
+
+* **You just use WireGuard** and want a safe default:
+  `sudo automtu` → picks `wg0 = egress_mtu - 80` (e.g., `1500 - 80 = 1420`).
+
+* **You suspect smaller upstream MTU** (PPPoE/ISP/VPN/“somewhere in the path”):
+  Use PMTU probing towards stable targets (your WG peer, DNS resolvers):
+
+  ```bash
+  sudo automtu --pmtu-target 46.4.224.77 --pmtu-target 1.1.1.1
+  ```
+
+  Then optionally apply the PMTU to your egress:
+
+  ```bash
+  sudo automtu --pmtu-target 46.4.224.77 --apply-egress-mtu
+  ```
+
+* **You have WireGuard peers** and want the tool to discover them automatically:
+  `sudo automtu --auto-pmtu-from-wg`
+  (You can still add manual targets and change policy.)
+
+---
+
+## How it works (short)
+
+1. **Egress detection**
+   Reads default routes and picks a non-VPN interface (e.g., `eth0`).
+   If you want to prefer `wg0` when the default route already uses it:
+
+   ```bash
+   sudo automtu --prefer-wg-egress --wg-if wg0
+   ```
+
+2. **PMTU probing (optional)**
+   Uses `ping -M do` (DF set) with a quick binary search to find the largest unfragmented payload for each target.
+   From the successful results, selects an **effective PMTU** using a policy:
+
+   * `--pmtu-policy min` (default, safest)
+   * `--pmtu-policy median`
+   * `--pmtu-policy max`
+
+3. **WireGuard MTU calculation**
+   `wg_mtu = max(wg_min, effective_mtu - wg_overhead)`
+   Defaults: `wg_min=1280`, `wg_overhead=80`.
+
+4. **Apply**
+
+   * If `--apply-egress-mtu` is set, apply **effective PMTU** to the egress (unless egress is `wg0`).
+   * Apply **WireGuard MTU** to `wg0` (or the iface passed via `--wg-if`).
+   * If `--set-wg-mtu X` is given, it **overrides** the computed value.
+
+---
+
+## Examples (copy & paste)
+
+### A) Quick WireGuard tuning with peer awareness
+
+```bash
+sudo automtu --auto-pmtu-from-wg
+```
+
+### B) Manual targets, conservative (min) policy
+
+```bash
+sudo automtu --pmtu-target 46.4.224.77 --pmtu-target 1.1.1.1
+```
+
+### C) Apply PMTU on egress + set matching wg0
+
+```bash
+sudo automtu --pmtu-target 1.1.1.1 --apply-egress-mtu
+```
+
+### D) Prefer WireGuard as egress (if default route uses WG)
+
+```bash
+sudo automtu --prefer-wg-egress --wg-if wg0 --auto-pmtu-from-wg
+```
+
+### E) Force a specific wg0 MTU
+
+```bash
+sudo automtu --set-wg-mtu 1372
+```
+
+### F) Dry-run any of the above
+
+```bash
+automtu --dry-run --auto-pmtu-from-wg --pmtu-target 1.1.1.1
+```
+
+---
+
+## Persisting the value in WireGuard
+
+Runtime changes are **not** permanent. To persist:
+
+* Either let your automation run this tool before/after `wg-quick up wg0`, **or**
+* Add a fixed value in your `wg0` config (`/etc/wireguard/wg0.conf`):
+
+  ```ini
+  [Interface]
+  MTU = 1372
+  ```
+
+  > Static MTU is fine if the path is stable. If your route/ISP changes, prefer running this tool.
+
+---
+
+## Notes & Troubleshooting
+
+* If **all PMTU probes fail**, the tool prints a warning and falls back to the egress MTU (e.g., `1500`) and sets `wg0 = egress - 80`.
+  Some networks block ICMP “fragmentation needed”; use multiple targets or rely on egress-only.
+* You can **override defaults** via flags or environment:
+
+  * `WG_IF=wg0 WG_OVERHEAD=80 WG_MIN=1280 automtu ...`
+* The tool **deduplicates targets** and understands IPv4/IPv6 endpoints (e.g., `2a01:...`).