Rules of etiquette change over time. The rule regarding congratulating a bride or bride-to-be is one of these. Brides and grooms may both be offered congratulations in the 21st century, although in some circles it is still considered bad manners to say congratulations to the bride. Choose wisely, considering the people around you, when deciding how best to offer your happy thoughts for a new bride.
Since Victorian times, etiquette has required that while congratulations are OK for a groom or groom-to-be, it is not proper to offer them to a bride or bride-to-be. This harks back to the days when a woman was considered the property of a man once he married her. Congratulating her on her engagement or wedding was the same as suggesting that she'd been hunting for a man and caught one. Instead, well-wishers congratulated the groom and offered the bride best wishes on her marriage.
It is no longer a breech of etiquette to offer congratulations to a bride, but many people are still uncomfortable with it. As such, it may be more comfortable to offer best wishes or another general term of hope to the wedding couple as a whole, rather than saying congratulations and risking insulting someone. Another option is to mention how touched you were by the ceremony and how happy you are for the couple.
The Reception Line
A large, formal wedding may have a reception line. As you walk down the line, you'll be introduced to each of the wedding party and their parents. Comment on how beautiful the bride looks and how happy you are for her, if you'd like to avoid congratulating her. You may offer your congratulations on the groom, or simply wish both he and the bride best wishes.
Written congratulations normally come in the form of a card that offers congratulations to both the bride and groom. When writing a personal note in the card, it is appropriate to let the couple know of your hopes for their happy future and to congratulate them on their marriage. Again, if you are concerned that congratulating the bride might cause ill feelings, simply offer your best wishes. The congratulatory letter should be addressed to both the bride and the groom if you are responding to an announcement.