Guide

How to match a browser's timezone and language to its proxy.

Sites can compare the location of your IP address with the timezone and language your browser reports. A German IP with a US clock and en-US is a strong sign of a proxy, even when nothing else leaks. Donut Browser sets each profile’s timezone and language from its proxy’s exit when it makes the profile, and checks the pair again before each launch. You need a profile with a proxy.

How Donut picks the values

When you create a profile with a proxy, Donut:

1. finds the proxy’s exit IP through the proxy, from public echo services such as api.ipify.org,
2. looks the IP up in a MaxMind GeoLite2 database on your computer, so the IP is not sent to a lookup service,
3. writes the exit’s IANA timezone (for example Europe/Berlin), its UTC offset, the latitude and longitude the database gives for the IP, and a language.

The language is a weighted random pick among the languages spoken in the exit’s country. The weights come from the share of people who speak each language, so a US exit gives en-US most of the time and es-US some of the time. The languages list holds the locale and its base language, for example de-DE and de.

This happens on every plan. In Create new profile, the box “Automatically configure location information based on proxy configuration or your connection if no proxy provided” must stay checked. It is checked by default.

The values stay fixed after that. Donut does not rewrite them when you change the profile’s proxy, so a mismatch shows up instead of being hidden.

1. Choose the proxy before you create the profile

1. Add and check the proxy on Network → Proxies. The check’s Connection details show the exit Timezone, so you know what the profile will get.
2. Click New on the Profiles page, choose the proxy in Create new profile, and create the profile.

For a WireGuard VPN, Donut cannot measure the exit at this point and writes no location. See step 5 of the WireGuard guide for the fix.

2. Keep the launch check on

Settings → Privacy → Block on fingerprint mismatch is on by default. Before a launch, Donut measures the exit of the profile’s proxy or VPN and compares:

Coordinates are not compared. The measured exit is kept for 30 minutes per proxy, so quick relaunches do not measure it again.

The check lets the launch go ahead without a verdict when the exit cannot be measured within 8 seconds, when the GeoIP database is missing, or when the proxy is Shadowsocks. Launches from the local API or MCP never block. They show a warning in the app instead.

3. Fix a mismatch with one click

When the values do not match, the launch stops with the dialog Launch blocked and the heading “The measured exit doesn’t match the fingerprint”. It names the problem, for example “Exit node is in Europe/Berlin but the fingerprint reports America/New_York.”

1. Click Match fingerprint to proxy. Donut writes the measured exit’s timezone, offset, coordinates and a new language into the profile.
2. Wait for “Fingerprint updated to match the proxy. Relaunch the profile to apply.” Donut cancels this launch.
3. Launch the profile again.

Match fingerprint to proxy works on every plan, also on Free and Solo, where you cannot edit the fingerprint by hand. It keeps the rest of the device.

The dialog has two other options. Launch anyway starts the browser with the mismatch. “Don’t block again for this exact mismatch” stops the dialog for this fingerprint and this exit until one of them changes. When you launch several profiles, “Apply this choice to the remaining profiles” uses your answer for all of them.

4. Check what sites see

Launch the profile and open What is my IP. It shows Timezone (from IP) next to Timezone (from browser), and a pair of clocks marked “Same time zone” or “Different time zones”.

You can also read the values in the browser’s DevTools console:

Intl.DateTimeFormat().resolvedOptions().timeZone; // "Europe/Berlin"
new Date().getTimezoneOffset();                    // -60 in winter, -120 in summer
navigator.language;                                // "de-DE"
navigator.languages;                               // ["de-DE", "de"]

A negative offset means the zone is ahead of UTC. Browser fingerprint shows the rest of the device.

When the values change by themselves

Three actions write a new location:

• Regenerate fingerprint in the profile’s Fingerprint section (Pro, Team and Enterprise) makes the new device from your own connection, not through the proxy. The next launch will likely block. Click Match fingerprint to proxy then.
• Generate random fingerprint on every launch measures the exit at each start and writes a matching location, together with a new device.
• Change IP on a rotating proxy can move the exit to another city or country. The launch check reuses the exit it measured in the last 30 minutes, so it can miss the move. Open What is my IP in the profile after a rotation. See How to rotate a proxy’s IP.

Set the location from the API

POST /v1/profiles reads the location through the proxy you pass in proxy_id, as the app does. To pin the location to a known IP, without a probe, pass it in wayfern_config.geoip. To turn location off, pass false.

curl -sS -X POST http://127.0.0.1:10108/v1/profiles \
  -H "Authorization: Bearer $DONUT_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"name": "DE shop", "browser": "wayfern", "proxy_id": "<proxy id>"}'

import os, requests

response = requests.post(
    "http://127.0.0.1:10108/v1/profiles",
    headers={"Authorization": f"Bearer {os.environ['DONUT_API_KEY']}"},
    json={
        "name": "DE shop",
        "browser": "wayfern",
        "proxy_id": proxy_id,
        "wayfern_config": {"geoip": "203.0.113.80"},  # optional: pin to this IP
    },
    timeout=60,
)
print(response.status_code, response.json())

PUT /v1/profiles/{id} cannot change the location. After a proxy change, launch the profile from the app and use Match fingerprint to proxy.

Troubleshooting

Related

• Profiles and fingerprints: the fingerprint values you can see and edit.
• Leak protection: the launch checks in Settings → Privacy.
• How to use a SOCKS5 proxy with a username and password
• How to rotate a proxy’s IP with a change-IP link

Donut Browser sets a matching timezone and language on every plan, including Free. Download it for macOS, Windows or Linux.

Last updated October 30, 2026.