Is there length limits on Token Symbols?

Question

Is there a limit on the length of a ERC20 Token symbol? I would like to use 4 letters, one of which is lower case, but that isn't an issue. My concern is if Exchanges have setup their tools to only handle 3 letters which is what most are today.

Answer 1

I used the CoinMarketCap API to pull down a list of all registered currencies and assets (so not just ERC-20 tokens... ), and fed it into a quick Python script to count the number of occurrences of symbols of different lengths.

import urllib, json
from collections import Counter

url = "https://api.coinmarketcap.com/v1/ticker/"
response = urllib.urlopen(url)
data = json.loads(response.read())

counts = Counter([len(asset['symbol']) for asset in data])
for i, j in sorted(counts.items()):
    print("Asset symbols of length %d: %d" % (i, j))

Gives the following counts:

Asset symbols of length 1: 3
Asset symbols of length 2: 35
Asset symbols of length 3: 639
Asset symbols of length 4: 273
Asset symbols of length 5: 121
Asset symbols of length 6: 18
Asset symbols of length 7: 2
Asset symbols of length 8: 4
Asset symbols of length 9: 3

So while the most common length is 3, you're probably good for longer lengths. Of course, different exchanges and websites may format their UIs differently...

Edit:

I was reminded of this thread by a newly posted question. (Naming conventions for ERC-20 instancies)

Running the script again, just for fun, as of 28 Nov 2017:

Asset symbols of length 1: 3
Asset symbols of length 2: 37
Asset symbols of length 3: 768
Asset symbols of length 4: 350
Asset symbols of length 5: 143
Asset symbols of length 6: 17
Asset symbols of length 7: 4
Asset symbols of length 8: 2
Asset symbols of length 9: 1

Answer 2

This same code for py 3.10 and new API coinmarket : 

from requests import Request, Session
from requests.exceptions import ConnectionError, Timeout, TooManyRedirects
from collections import Counter
import json

url = 'https://pro-api.coinmarketcap.com/v1/cryptocurrency/map'  
parameters = {
  'start':'1',
  'limit':'5000',
}  
headers = {
  'Accepts': 'application/json',
  'X-CMC_PRO_API_KEY': 'Your-Coin-Market-API-Key ;-)',
}

session = Session()
session.headers.update(headers)

try:  
  response = session.get(url, params=parameters)
  data = json.loads(response.text)

  counts = Counter([len(asset['symbol']) for asset in data['data'] ])

  for i, j in sorted(counts.items()):  
        print("Asset symbols of length %d: %d" % (i, j))  

except (ConnectionError, Timeout, TooManyRedirects) as e:  
  print(e)

result at 2021-12-30 :

Asset symbols of length 5: 609
Asset symbols of length 6: 168
Asset symbols of length 7: 100
Asset symbols of length 8: 57
Asset symbols of length 9: 25
Asset symbols of length 10: 9
Asset symbols of length 11: 2
Asset symbols of length 12: 3
Asset symbols of length 13: 1
Asset symbols of length 23: 1