What the copper IUD is and how it works
The copper IUD is a small, long-acting, non-hormonal contraceptive device placed inside the uterus. It is one of the most effective forms of birth control available, and it works without releasing hormones into your body (Wikipedia: Copper IUD). Because it contains no hormones, the mechanism is local: the copper in the device affects the environment in the uterus rather than changing your hormonal cycle.
That non-hormonal design is the condition that changes who finds it appealing. If you have had trouble with hormonal methods. Or simply want to avoid them. The copper IUD is the option that keeps contraception separate from your hormones. It is also long-acting, so it does not depend on remembering a daily pill or a routine before sex (Wikipedia: Copper IUD). The trade-off is that its effects are concentrated in the uterus. Is why the side-effect profile below centres on bleeding and cramps rather than hormonal symptoms.
How effective it is
The copper IUD is one of the most effective forms of birth control available (Wikipedia: Copper IUD). That is the headline figure you can rely on when weighing it against other methods: it sits at the top tier of contraceptive effectiveness rather than in the middle.
Effectiveness is not the only question, though. The same source notes it can also be used for emergency contraception within five days of unprotected sex (Wikipedia: Copper IUD). So the device serves two roles. Ongoing contraception and a post-sex backup. And knowing that changes how you might think about timing if you are considering it after unprotected sex.
How it is fitted and used
Fitting is a procedure carried out by a clinician: the device is placed inside the uterus. The practical routine after that is simple. There is nothing to do day to day. Is the point of a long-acting method (Wikipedia: Copper IUD).
The condition that changes the fitting picture is timing around pregnancy and birth. The device may be used for contraception regardless of your age or whether you have been pregnant before, and it may be placed immediately after a vaginal delivery, a caesarean delivery, or a surgical abortion (Wikipedia: Copper IUD). That means a recent birth or abortion does not automatically rule out fitting; it can be part of the same episode of care. The NHS page on the IUD is the practical destination for who can use it and what fitting involves (NHS: IUD (copper coil)).
Side effects to expect
The main side effect is a change in your periods: common side effects include heavy menstrual periods and increased menstrual cramps, also called dysmenorrhoea (Wikipedia: Copper IUD). This is the specific thing to plan around, because it is the effect most people notice.
Because those effects are tied to menstruation, the trade-off is clearest for anyone whose periods are already heavy or painful. The device can make that pattern more pronounced. That is the concrete detail that should shape your expectations rather than a vague warning: expect heavier bleeding and stronger cramps as the documented common effects, and weigh that against the method’s effectiveness and its hormone-free design (Wikipedia: Copper IUD).
Who it suits
It suits people who want a highly effective, non-hormonal, long-acting method and who are willing to accept heavier, more crampy periods as the trade-off (Wikipedia: Copper IUD). It also suits people who need contraception regardless of age or previous pregnancy, including around delivery or abortion, since fitting can happen in those settings (Wikipedia: Copper IUD).
If heavy periods or cramps would be a serious problem for you, that is the condition that should push you toward a conversation about alternatives rather than an assumption that the copper IUD is the default. The fit question is really a comparison: top-tier effectiveness and no hormones on one side, heavier and more painful periods on the other (Wikipedia: Copper IUD).
If something goes wrong or you are unsure
If you are unsure whether it suits you, or you want the practical detail on fitting and who can use it, the NHS IUD page is the place to check (NHS: IUD (copper coil)). For the emergency-contraception use, the relevant window is within five days of unprotected sex (Wikipedia: Copper IUD). Timing is the thing to act on quickly rather than waiting.
As a practical boundary: this page gives you the mechanism, the effectiveness, the fitting routine, the main side effect, and who it tends to suit. The decision about your own body belongs in a conversation with a clinician who can assess your situation. Use the NHS page to prepare for that conversation, and treat fitting as a clinical procedure rather than something to arrange on your own (NHS: IUD (copper coil)).