To show HTML text on UILabel we need to convert the text to NSAttributedString. To achieve this we can use following code:

        if let htmlData = htmlString.data(using: String.Encoding.utf16, allowLossyConversion: false) {
            if let attributedString = try? NSMutableAttributedString(data: htmlData, options: [NSDocumentTypeDocumentAttribute: NSHTMLTextDocumentType], documentAttributes: nil) {
                label.attributedText = attributedString
            }
        }

We can also make an extension on String class like so:

extension String {
    func attributedString() -> NSAttributedString? {
        if let htmlData = self.data(using: String.Encoding.utf16, allowLossyConversion: false) {
            if let attributedString = try? NSMutableAttributedString(data: htmlData, options: [NSDocumentTypeDocumentAttribute: NSHTMLTextDocumentType], documentAttributes: nil) {
                return attributedString
            }
        }
        return nil
    }
}

In Objective-C following method can be used:

- (NSAttributedString *)attributedStringFromHtml:(NSString *)htmlString {
    NSData *data = [htmlString dataUsingEncoding:NSUTF16StringEncoding allowLossyConversion:false];
    NSError *err;
    NSAttributedString *attr = [[NSAttributedString alloc] initWithData:data options:@{NSDocumentTypeDocumentAttribute:NSHTMLTextDocumentType} documentAttributes:nil error:&err];
    if (err) {
        NSLog(@"Error while converting: %@",err.localizedDescription);
    }
    return attr;
}