You need to be an admin to create a username for your Page. Your Page’s username will appear below your Page’s name and in your Page’s URL.

Requirements:

• Length: at least 5 characters long;
• Restricted symbols or punctuation: Usernames can only contain alphanumeric characters (A–Z, 0–9) and periods (“.”). They can’t contain generic terms or extensions (.com, .net). Periods (“.”) and capitalization can’t be used to differentiate usernames. For example, johnsmith55, John.Smith55 and john.smith.55 are all considered the same username.

Note: Keep in mind that new Pages may not immediately be able to create a username, and that your Page’s username may be removed because of inactivity.

• Length: cannot be longer than 20 characters;

Note: To create a custom URL for your channel, your account needs to meet the following requirements:

• Have 100 or more subscribers
• Be at least 30 days old
• Have an uploaded photo as channel icon
• Have uploaded channel art

In general, a YouTube channel may only have one (1) custom URL and custom URLs cannot be transferred or assigned to anyone.

• Length: cannot be longer than 30 characters;
• Restricted symbols or punctuation: Username must contains only letters, numbers, periods and underscores.

Requirements:

• Length: cannot be longer than 15 characters;
• Restricted symbols or punctuation: A username can only contain alphanumeric characters (letters A-Z, numbers 0-9) with the exception of underscores.

Requirements:

• Length: 3-20 characters;
• Restricted symbols or punctuation: Any character from, A-Z, a-z, 0-9, _ and – is valid.

Requirements:

• Length: 3-30 characters;
• Restricted symbols or punctuation: Your username can’t have spaces, symbols or punctuation.

Unknown requirements.

• Length: Up to 32 characters.
• Restricted symbols or punctuation: anything that’s not a letter, number, or a dash/hyphen is not allowed.

• Length: Flickr recommends your screen name to be no more than 20 characters.
• Restricted symbols or punctuation: Your alias can only contain letters, numbers, “_” or “-“.

Note: Please note that your screen name and Alias (URL) are changed separately.

• You have ten or more followers (people who have added you to their circles)
• Your account is at least 30 days old
• Your profile has a profile photo
• Your account is in good standing

Note: Custom URLs must meet the Google+ User Content and Conduct Policy and the Google+ custom URLs terms of use.

• Company Name Length: 100 maximum characters

• Local Business or Place
• Company Organization or Institution
• Brand or Product
• Artist, Band or Public Figure
• Entertainment
• Cause or Community

Click here to check out the available Facebook page categories for each type of page.

Note: Please note that the category you pick can later be changed from the About section of your page and there will be a ton of other categories to pick from.

• Standard
• YouTube Red

However, as a creator or brand channel, you do not need to join the paid YouTube Red. Your videos will automatically shown to YouTube Red subscribers, while creating a secondary revenue stream in addition to what you will be earning through regular ads. Meaning that there is no need for you to pick a specific category or channel type on Youtube.

Nevertheless, I should as well note that there is a difference between:

• youtube.com/USER/yourhandle
• youtube.com/CHANNEL/yourhandle

When you first create a YouTube profile, you will start off as a “user” and then you will need to as well create a “channel”. More about this you can read in YouTube’s Creators Forum.

Instagram Business Accounts can pick from the following main categories:

• Books & Magazines
• Brands & Products
• Companies & Organizations
• Event Sources
• Local Businesses
• Movies
• Music
• Other
• People
• Sports
• Television
• Websites & Blogs

Each of these categories have subcategories to pick from.

Once you create or convert to a Business Profile on Pinterest, you can pick from the following Pinterest Business Types:

• Brand
• Institution/Non-profit
• Local Business
• Media
• Online Marketplace
• Other
• Professional
• Public figure
• Retailer

Nevertheless, ASKfm launched verified accounts – to verify celebrities and other well-known brands.  Click here to check out what are the criteria for getting a verified blue badge on ASKfm .

The company types that you need to pick from are:

• Public Company
• Educational Institution
• Self-employed
• Government Agency
• Nonprofit
• Sole Proprietorship
• Privately Held
• Partnership

Afterward you will pick a industry from almost a hundred options.

• Profile Photo:
  • Recommended: 250×250 pixels;
  • Displays at 170×170 pixels on your Page on computers, 128×128 pixels on smartphones and 36×36 pixels on most feature phones
• Cover Photo:
  • Recommended: 820 pixels wide by 462 pixels tall;
  • Displays at 820 pixels wide by 312 pixels tall on your Page on computers and 640 pixels wide by 360 pixels tall on smartphones
  • Must be at least 400 pixels wide and 150 pixels tall
  • Loads fastest as an sRGB JPG file that’s 851 pixels wide, 315 pixels tall and less than 100 kilobytes

Details about Facebook Profile and Cover photos specs here.

• Profile Photo:
  • Recommended: 800 X 800 px image;
  • Square or round image that renders at 98 X 98 px;
  • JPG, GIF, BMP, or PNG file (no animated GIFs);
• Cover Photo:
  • Recommended: 2560 x 1440 px;
  • Important: Channel art looks different on desktop, mobile, and TV displays — larger images may be cropped.
  • Minimum dimension for upload: 2048 x 1152 px.
  • Minimum safe area for text and logos: 1546 x 423 px. Larger images may get cropped on certain views or devices.
  • Maximum width: 2560 x 423 px. This means that the “safe area” is always visible regardless of screen size. The areas to each side of the channel art are visible or cropped depending on browser size.
  • File size: 4MB or smaller.

Details about YouTube Channel Icon Specs here.

Details about YouTube Channel Art Specs here.

• Profile Photo:
  • Recommended: 250×250 px;

• Profile Photo:
  • Recommended: 400×400 px;
  • Photos can be in any of the following formats: JPG, GIF, or PNG. (Twitter does not support animated GIFs for profile or header images.)
• Cover Photo:
  • Recommended: 1500×600 px;
  • Photos can be in any of the following formats: JPG, GIF, or PNG. (Twitter does not support animated GIFs for profile or header images.)

Details on Twitter Photo and Cover photo specs here.

• Profile Photo:
  • Recommended: Square format 130px or above;

• Profile Photo:
  • Recommended: 600x600px;
  • Displays as 165x165px;

• Profile Photo:
  • Recommended: Suare format 250px;
• Background Photo:
  • Recommended: 1680×1050 px;

• Profile Photo:
  • Recommended: Square image 250px and higher;
  • Displays at 128px x 128px;
• Cover Photo:
  • Recommended: 1600x900px;

• Profile Photo:
  • Recommended: 300×300 px;
  • Displays at 300x300pc to 48×48 pixels;

• Profile Photo:
  • Recommended: 1000×1000 px for best quality;
  • Displayed as 250 x 250 px;
• Cover Photo:
  • Recommended: 1600 x 900 px;
  • The minimum size of the cover image must be more than 480 x 270 px.

• Profile Photo:
  • Recommended: 300x300px;
• Cover Photo:
  • 1536×768 px;

Details about LinkedIn’s Photo and Cover photo specs here. 

• About Section Length:
  • Short Description: 255 bytes(characters) limit;
  • Impressum: 2,000 characters limit;
• Website: Yes, there is a field where you can add a link to your website;
• Contact details: Yes, you can add phone, email and location;
• Other Social Profiles: Yes, you can add links to your:
  • Instagram
  • Twitter
  • Snapchat
  • YouTube
  • Twitch
  • LINE
  • WeChat
  • Kik

• Channel Description Length: up to 1000 characters;
• Website: Yes, you can add up to 5 custom links to your profile;
• Contact details: You can add your country and contact email address;
• Other Social Profiles: You can add up to 5 custom links to your profile; If you add your website, you can add 4 social network links;

• Bio Section Length: up to 150 characters;
• Website: Yes, you can add one link in your Bio section. Here you can add your website link.
• Contact details: You can add your business email and phone numbers as well as your business location.
• Other Social Profiles: You can link your profile to the below listed social media, however, the links will not be visible to your followers:
  • Facebook
  • Twitter
  • Tumblr
  • Ameba
  • OK.ru

• Bio Section Length: maximum 160 characters;
• Website: Yes, you can add your website (or another link) in your profile About section;
• Contact details: You can add your location;
• Other Social Profiles: No specific field for other social profiles, however, you can use the link space in your About section;

• About Section Length: N/A
• Website: N/A
• Contact details: N/A
• Other Social Profiles: N/A

• About Section Length: Up to 160 characters;
• Website: Yes, there is a field where you can add your website;
• Contact details: You can add your location;
• Other Social Profiles: Yes, you can connect the following social media network to your account, however, these links will not be visible to your audience:
  • Facebook
  • Twitter
  • Google+
  • Gmail, Yahoo, Microsoft

• Bio Section Length: up to 300 characters;
• Website: Yes, there is a field where you can add your website;
• Contact details: You can add your location;
• Other Social Profiles: In the “Web” field where you can add your website, you can as well add links to your other websites or social media. However the character space is limited to 146 characters, and you can add on average 4 links in total.

• About Section Length: Unlimited (depends on your theme)
• Website: Depending on your theme, you can add as much information as you want;
• Contact details: Depending on your theme, you can add as much information as you want;
• Other Social Profiles: Depending on your theme, you can add as much information as you want;

• About Section Length: Unlimited;
• Website: Yes, there is a field where you can add your website link;
• Contact details: You can add your email address and location;
• Other Social Profiles: Yes, you can add links to:
  • Facebook
  • Twitter
  • Instagram
  • Pinterest
  • Tumblr

• About Section Length: Unlimited;
• Website: Yes, there is a field where you can add your website;
• Contact details: You can add your phone, email, Address and chat links (Skype, Yahoo, AIM, GoogleTalk, ICQ, Jabber, MSN, Net Meeting, QQ);
• Other Social Profiles: Yes, there are unlimited fields for extra link to add;

• About Section Length: Up to 2,000 characters;
• Website: Yes, there is a field where you can add your website link;
• Contact details: You can add your company location;
• Other Social Profiles: N/A