# Proxy format: ip:port:username:password explained

> The usual proxy format is ip:port:username:password. The same four values also come as username:password@ip:port, with or without a scheme in front.

Source: https://mosaicbrowser.com/guides/proxy-format-ip-port-username-password

## Proxy format: ip:port:username:password explained

A proxy with a login is most often written ip:port:username:password, for example 203.0.113.24:8080:user:pass. The same four values also appear as username:password@ip:port, with a scheme such as http:// or socks5:// in front when the tool needs to know the protocol.

![ip:port:username:password, and the other shapes, beside a screenshot: bulk-importing proxies into Mosaic: every line read, new and duplicate ones told apart](https://mosaicbrowser.com/covers/proxy-format-ip-port-username-password.webp)

Every proxy with a login comes down to four values: the host (an IP address or a hostname), the port, the username and the password. The most common proxy format writes them as ip:port:username:password, and every other format is only a different order or a different separator. Sellers' dashboards export a handful of shapes, and most problems people hit come from pasting one shape into a tool that expects another.

## Proxy formats with ip, port, username and password

The examples use 203.0.113.24, an address reserved for documentation, with `user` and `pass` as the login.

| Format | Example | Where you meet it |
| --- | --- | --- |
| `ip:port:username:password` | `203.0.113.24:8080:user:pass` | the most common export from seller dashboards |
| `username:password@ip:port` | `user:pass@203.0.113.24:8080` | curl, scripts, many browser extensions |
| `scheme://username:password@ip:port` | `socks5://user:pass@203.0.113.24:1080` | anything that needs the protocol spelled out |
| `username:password:ip:port` | `user:pass:203.0.113.24:8080` | some dashboards, reversed |
| `ip:port@username:password` | `203.0.113.24:8080@user:pass` | some dashboards, reversed |
| `ip:port` | `203.0.113.24:8080` | proxies with no login, allowed by your IP instead |

A reader can tell `ip:port:username:password` from `username:password:ip:port` by where the number sits. A port is a number from 1 to 65535 and a password usually is not, so the field that is a port marks where the address is. That is the rule Mosaic's importer uses, and it is why a numeric password, like `user:12345`, can still confuse a careless one.

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[How it works: Provider minting](https://mosaicbrowser.com/features/proxy-providers)

## What the format leaves out

The colon format has no place for the protocol. A line like `203.0.113.24:1080:user:pass` might be HTTP or SOCKS5, and the line cannot tell you. Pick the type yourself, or rewrite the line as a URL with `http://` or `socks5://` in front.

Getting this wrong does not fail where you would expect. We met it with Cat Proxies, whose ports name the protocol: 9000, 10000 and 12000 answer HTTP and 11000 answers SOCKS5. A batch of 11000 lines imported as HTTP looked fine in the list and failed at launch, one profile at a time. Mosaic now reads the port on that seller's lines, and a proxy check before first use catches the rest.

Chrome adds one more limit. Its `--proxy-server` flag takes `scheme://host:port` only, and Chromium's documentation says Chrome "will not use any credentials embedded in the proxy settings" ([proxy.md](https://chromium.googlesource.com/chromium/src/+/HEAD/net/docs/proxy.md), read 2 November 2026). For HTTP proxies Chrome asks for the login in a box; for SOCKS5 it cannot send one at all, which [Chrome SOCKS5 proxy with username and password](https://mosaicbrowser.com/guides/chrome-socks5-proxy-with-username-and-password) works through.

## When the username carries options

With a residential seller the username is rarely just a name. It carries the country, sometimes a city, and the session id that keeps one exit. Oxylabs' example is `customer-USERNAME-cc-DE-sessid-abcd1234`, with the password on its own ([Oxylabs session control](https://developers.oxylabs.io/products/proxies/residential-proxies/session-control)). IPRoyal puts the options in the password instead: `password321_country-br_session-sgn34f3e_lifetime-10m` ([IPRoyal rotation docs](https://docs.iproyal.com/proxies/residential/proxy/rotation)).

Either way the format stays the same four values. What changes is that two lines differing by one token are two different proxies, and usually two different exits. The session token is what decides rotating against sticky behaviour, which [rotating vs sticky proxies](https://mosaicbrowser.com/guides/rotating-vs-sticky-proxies) covers seller by seller.

## Converting between formats

For a few lines, a text editor's find and replace does the job. For a list, check two things after converting: that no password containing a colon or an `@` was split in the wrong place, and that the protocol survived. Then check one proxy from the list before using any, the way [how to check a proxy before you use it](https://mosaicbrowser.com/guides/how-to-check-a-proxy-before-you-use-it) describes, because a list that converts cleanly can still point at the wrong port.

## Pasting a list into Mosaic

Mosaic reads every shape in the table above, so there is nothing to convert first.

1. Open Proxies › **Bulk import**, then paste the list or open a .txt or .csv file.
2. Read the preview. Each line is marked **New**, **Already there** or **Unread**, and an unread line says why, so one bad line does not sink the rest.
3. Leave **Check each after import** on. Mosaic checks six at a time and names the ones that do not answer.
4. Press **Import**.

![Bulk-importing proxies into Mosaic: every line read, new and duplicate ones told apart](https://mosaicbrowser.com/shots/proxy-import.png)
*Eight lines in mixed formats, read one by one*

A CSV or TSV with a header row works too, with columns found by name, such as `host`, `port`, `username`, `password`, `type` and `country`. A trailing `|US` on a plain line records the country the seller says it is in. Proxies export back out as URLs, colon lines or CSV, in a form the importer reads again. If your seller sells one gateway line rather than a list, save it as a provider instead, as [the proxy providers page](https://mosaicbrowser.com/features/proxy-providers) explains.

## Sources

1. [Chromium: Proxy support in Chrome (net/docs/proxy.md)](https://chromium.googlesource.com/chromium/src/+/HEAD/net/docs/proxy.md), read November 2, 2026
2. [Oxylabs Developers: Residential proxies session control](https://developers.oxylabs.io/products/proxies/residential-proxies/session-control), read November 2, 2026
3. [IPRoyal Docs: Residential proxy rotation](https://docs.iproyal.com/proxies/residential/proxy/rotation), read November 2, 2026

## Questions

### What is the difference between ip:port:user:pass and user:pass@ip:port?

Nothing in the proxy itself. Both carry the same four values; they are two ways of writing them down. Which one to use depends on what the tool you paste into reads.

### Where does the proxy type go in ip:port:username:password?

Nowhere. The colon format has no field for HTTP or SOCKS5, so you choose the type separately or write the line as a URL, such as socks5://user:pass@203.0.113.24:1080.

### Can a proxy password contain a colon?

It can, and it makes the colon format ambiguous. The @ form is safer in a reader like Mosaic's, which ends the username at the first colon and starts the address after the last @, so the rest of the password stays whole.

### Why is my proxy username so long?

Residential sellers write options into the username: country, city, session id and how long the session lasts. The whole string is the username, and changing one token inside it changes where the proxy exits.

## Related

[Chrome SOCKS5 proxy with username and password](https://mosaicbrowser.com/guides/chrome-socks5-proxy-with-username-and-password): A Chrome SOCKS5 proxy with username and password fails: Chromium has no SOCKS5 sign-in. Use the seller's HTTP port, allowlist your IP, or relay it.

[Rotating vs sticky proxies: which one an account needs](https://mosaicbrowser.com/guides/rotating-vs-sticky-proxies): Rotating vs sticky proxies: rotating changes the exit IP per connection, sticky keeps one for a session you name. Logged-in accounts need sticky.

[How to use a different proxy for each Chrome profile](https://mosaicbrowser.com/guides/use-a-different-proxy-for-each-chrome-profile): Chrome has no proxy setting per profile. Use a proxy extension in each profile, or launch Chrome with its own data folder and --proxy-server.

[How to check a proxy before you use it](https://mosaicbrowser.com/guides/how-to-check-a-proxy-before-you-use-it): Check that a proxy answers and tunnels, where its exit really is, whether the address is residential or blocklisted, and that the browser stays behind it.

[Provider accounts: one gateway line, one exit per profile](https://mosaicbrowser.com/features/proxy-providers): Paste your proxy seller's gateway line once and Mosaic mints a separate session for every profile, so each one browses from its own exit address.

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## Run this guide on your own accounts

Every Mosaic profile is a fingerprint, a proxy exit and a cookie jar that agree with each other, kept on your computer. Free holds 3 profiles. Pro is $49 a month for any number.

Mosaic is a desktop app

Email yourself the link and open it on your computer.