You've picked a great username. It's short, memorable, and fits your brand. Then you try to register it on Depop and get rejected — turns out it has an underscore, and Depop doesn't allow those. Every reselling platform has its own set of rules for usernames, and they're more different than you'd expect.
Here's a platform-by-platform breakdown of what's actually allowed. If you're still deciding on a name, start with our guide to choosing the right username for your reselling brand.
eBay
eBay gives you the most room to work with.
- Length: 6 to 64 characters
- Allowed: Letters, numbers, hyphens (-), underscores (_), periods (.), and asterisks (*)
- Not allowed: Spaces, consecutive underscores, the word "eBay," domain extensions (.com, .net), or starting with a special character
- Case sensitive: No — "ThriftKing" and "thriftking" are the same account
- Can you change it? Yes, once every 30 days
eBay is the most flexible platform for username formatting. If your name works on eBay, that doesn't mean it'll work everywhere else.
Poshmark
Poshmark keeps it tight.
- Length: Up to 15 characters
- Allowed: Letters, numbers, and underscores
- Case sensitive: No
- Can you change it? Yes, but only 2 to 3 times — ever. Changes require phone verification via SMS and must be done on the website, not the app.
That lifetime change limit makes Poshmark the platform where your first choice matters most. Get it right the first time.
Depop
Depop has the strictest rules of any platform on this list.
- Length: Minimum 3 characters
- Allowed: Lowercase letters and numbers only — no underscores, no hyphens, no periods, no special characters of any kind
- Case sensitive: Forced lowercase — you can't use capital letters at all
- Can you change it? Yes, once every 30 days
If your ideal username uses underscores or hyphens to separate words, you'll need a Depop-specific alternative. "thrift_queen" becomes "thriftqueen" here.
Etsy
Etsy has a shop name (what appears in your shop URL) and a username (your account ID). Since buyers find you by shop name, those are the rules that matter most.
- Length: 4 to 20 characters
- Allowed: Letters and numbers only — no spaces, underscores, hyphens, or special characters
- Case sensitive: No, but capitalization is displayed as you enter it (so "VintageFinds" looks better than "vintagefinds" in your shop URL)
- Can you change it? Yes, up to 5 times through the built-in system. After that, you need to contact Etsy support. Old shop names can't be reused, even from closed shops.
Grailed
Grailed is the least documented platform when it comes to username rules.
- Length: Not officially published
- Allowed: Letters, numbers, and likely underscores and hyphens based on existing profiles
- Case sensitive: Not documented
- Can you change it? Yes, through Settings with no documented limit on frequency
Grailed's validation rules are only visible when you actually try to create or change a username. If you're unsure whether a format will work, try it — Grailed will tell you in real time.
Vinted
Vinted enforces lowercase and has a few formatting restrictions.
- Allowed: Lowercase letters, numbers, periods (.), hyphens (-), and underscores (_)
- Not allowed: Starting or ending with a hyphen or underscore, emojis, or spaces
- Case sensitive: Lowercase only — everything displays in lowercase regardless of what you type
- Can you change it? Yes, once every 30 days, and not while you have active orders. Your old username becomes available for someone else to claim.
Mercari
Mercari has clear, well-documented rules.
- Length: 6 to 20 characters
- Allowed: Lowercase letters, numbers, hyphens (-), underscores (_), and periods (.)
- Not allowed: Capital letters, or starting/ending with a special character. No consecutive special characters.
- Case sensitive: Lowercase only
- Can you change it? Yes, anytime, as long as you don't have pending transactions. No limit on how often.
Mercari also separates "username" (your unique @handle) from "profile name" (a display name that can include emojis and special characters). The username is what matters for branding.
The Compatibility Problem
Here's where it gets tricky. A username that works on one platform might be invalid on another:
- Underscores and hyphens work on eBay, Poshmark, Vinted, and Mercari — but not on Depop or Etsy
- Periods work on eBay, Vinted, and Mercari — but not on Poshmark, Depop, or Etsy
- Capital letters work on eBay, Poshmark, and Etsy — but Depop, Vinted, and Mercari force lowercase
- Short names (under 4 characters) only work on Depop — every other platform requires at least 4 to 6
If you want the same username everywhere, your safest bet is lowercase letters and numbers only, between 6 and 15 characters. That format is accepted on every platform.
Quick Reference
| Platform | Length | Letters | Numbers | _ - . | Case | Changes |
|---|---|---|---|---|---|---|
| eBay | 6-64 | Yes | Yes | Yes | Any | Every 30 days |
| Poshmark | Up to 15 | Yes | Yes | _ only | Any | 2-3 lifetime |
| Depop | 3+ | Lowercase | Yes | No | Lowercase | Every 30 days |
| Etsy | 4-20 | Yes | Yes | No | Any | Up to 5 times |
| Grailed | Undocumented | Yes | Yes | Likely | Undocumented | Anytime |
| Vinted | Undocumented | Lowercase | Yes | Yes | Lowercase | Every 30 days |
| Mercari | 6-20 | Lowercase | Yes | Yes | Lowercase | Anytime |
Before You Commit
Run your username through this checklist:
- 6 to 15 characters? Fits every platform's limits
- Lowercase letters and numbers only? Works everywhere without modification
- No special characters? Avoids Depop and Etsy rejections
- Available on all your platforms? Check with Username Inspector
The rules won't change how you pick a great name — but knowing them will save you from the frustration of finding out your perfect username doesn't work on the one platform you forgot to check. Ready to verify availability? Check all 11 platforms at once with Username Inspector.