Key Lime Bars are one of my favorite ways to get that classic key lime pie flavor in a form that’s easy to slice and share. You get a buttery graham cracker crust and a bright, tangy filling that sets up into a creamy custard.
I like these bars because the texture stays smooth and thick, not runny, and the lime comes through clearly. The filling is rich from condensed milk, but the citrus keeps it tasting clean and sharp.
For me, these are best served well chilled, especially for warm-weather gatherings or anytime you want a dessert that holds up on a platter. I usually finish them with whipped cream and a little extra zest when I want them to look a bit more “finished.”
Why You’ll Love This Recipe
Classic flavor: It has that familiar key lime pie taste—tangy, creamy, and a little sweet—without needing anything fancy.
Easy crust: Graham cracker crust is quick to throw together and bakes up crisp enough to slice cleanly.
Reliable set: The custard firms up nicely in the fridge, so you get neat bars instead of a messy scoop-and-serve situation.
Make-ahead friendly: These are better after a chill, which means you can make them earlier and forget about dessert until you’re ready to slice.
Simple to serve: A dollop of whipped cream and a little zest is really all you need, and they look great on a dessert tray.
Ingredients You’ll Need
Graham Cracker Crust
- Graham cracker crumbs: I use plain graham crackers crushed into fine crumbs. Digestive biscuits work too if that’s what you have.
- Granulated sugar: Just enough to lightly sweeten the crust and help it brown a bit in the oven.
- Unsalted butter: Melted butter is what makes the crust pressable and crisp. If you only have salted butter, just ease up on the added salt.
- Fine salt: Don’t skip it—the crust tastes flatter without that little bit of salt.
Key Lime Filling
- Sweetened condensed milk: This is what makes the filling creamy and rich, and it also brings the sweetness. Make sure it’s sweetened condensed milk, not evaporated milk.
- Egg yolks: Yolks help the filling set into that smooth custard texture. Save the whites for an omelet or meringues.
- Key lime juice: Bottled key lime juice is really consistent, and I use it often when key limes aren’t easy to find. Fresh regular lime juice also works well.
- Lime zest: Fresh zest makes the lime flavor pop. I zest right before mixing so it doesn’t dry out.
- Fine salt: A small amount keeps the filling from tasting one-note sweet.
Optional Topping
- Whipped cream: I like a soft, lightly sweet whipped cream here. It’s an easy way to mellow the tartness.
- Extra lime zest: A little sprinkle right before serving looks nice and adds a fresh lime smell.
Recipe Instructions
- Preheat the oven: Heat the oven to 350°F. Line a 9×13-inch pan with parchment paper, leaving some overhang on the long sides, then lightly grease it.
- Mix the crust: Stir the graham cracker crumbs, sugar, melted butter, and salt together until the crumbs are evenly moistened.
- Bake the crust: Press the crust mixture firmly into an even layer in the pan. Bake for about 10 to 12 minutes, until lightly golden.
- Whisk the filling: Whisk the sweetened condensed milk and egg yolks in a bowl until smooth.
- Add the lime: Whisk in the lime juice, lime zest, and salt until the mixture thickens slightly.
- Bake the bars: Pour the filling over the hot crust and spread it into an even layer. Bake for about 14 to 18 minutes, until the edges are set and the center still has a slight jiggle.
- Cool: Let the pan cool at room temperature for about 30 minutes.
- Chill: Refrigerate for at least 2 hours (or overnight) until fully cold and firm.
- Slice and serve: Lift the bars out using the parchment, then slice with a warm, clean knife. Serve chilled with whipped cream and extra lime zest if you want.
Some of my tips!
This is the part that really makes a difference. If you only read one section, make it this one because this is where I share the little trick that helps the recipe turn out so well.
Recipe Tips & Tricks
Use parchment with a good overhang. It makes it so much easier to lift the whole slab out for clean slicing. I like leaving extra on the long sides so I have something sturdy to grab.
Press the crust firmly. Get it packed in tight, especially around the edges. A flat-bottomed measuring cup works well for this.
Don’t overbake the filling. You’re looking for set edges and a center that still jiggles a little. It will firm up a lot more as it cools and chills.
Chill longer for cleaner slices. Two hours works, but if you have the time, overnight is even better. The colder the bars, the neater the cut.
Warm the knife and wipe between cuts. A warm, clean knife helps you get those tidy squares. I usually run it under hot water, wipe it dry, then slice.
Add cornstarch if you need extra firmness. If you’re transporting these and want them to hold up a bit more, whisk 1 tablespoon cornstarch into the filling.
Make some touches!
There are plenty of easy ways to serve this depending on the occasion. Keep it simple, or add a few small touches to make it feel a little more special.
Serving Suggestions
- Whipped cream: A simple dollop on each bar is my go-to. You can sweeten it lightly or keep it plain.
- Extra lime zest: Zest right over the top right before serving. It makes them smell fresh and looks nice too.
- Fresh berries: Strawberries, raspberries, or blueberries are easy on the side. I like this when I’m serving a dessert plate.
- Iced coffee or hot coffee: These are great with coffee, especially if you like a tart dessert with a bitter drink. I usually go with iced coffee in the summer.
Save it for later
This section covers how to store leftovers and what parts of the recipe you can prepare ahead of time.
Storage and Make Ahead
Store leftovers covered in the fridge for up to 4 days. I keep them right in the pan with plastic wrap, or move slices to an airtight container.
You can make this recipe ahead the day before and slice it when you’re ready to serve. I actually prefer them after an overnight chill because the filling firms up more.
If you want them to last longer, you can freeze individual portions or freeze the whole slab (once fully chilled) wrapped well. Thaw in the fridge overnight before serving.
A few quick answers
This section covers a few extra details that may help before you head to the recipe card.
Recipe FAQs
Can I use regular limes instead of key limes?
Yes. Fresh lime juice works well here, and it still tastes like a classic lime bar. Bottled key lime juice is also a good option when key limes aren’t available.
How do I know when the bars are done baking?
The edges should look set, and the center should still have a slight jiggle when you gently shake the pan. If the center looks wet and sloshy, give it a few more minutes.
Why did my filling crack?
Cracks usually come from baking a little too long or cooling too fast. It’s not a big deal for taste—whipped cream on top covers a lot.
Can I make these firmer for transporting?
Yes. You can whisk 1 tablespoon cornstarch into the filling for a slightly firmer set, and I’d also chill them longer before slicing and packing them up.
Can I swap digestive biscuits for graham crackers?
You can. Use the same volume of crumbs, and the crust will bake up very similarly. The flavor is a little different, but it works.
You might also like
Before you go, take a look at a few other recipes below the recipe card. They use similar ingredients in a different way and are worth saving too.
MORE DINNER RECIPES TO TRY
Key Lime Bars
INGREDIENTS
Graham Cracker Crust
- 2 cups graham cracker crumbs
- ¼ cup granulated sugar
- ¾ cup unsalted butter melted
- ¼ tsp fine salt.
Key Lime Filling
- 2 cans sweetened condensed milk 14 oz each
- 6 large egg yolks
- ¾ cup key lime juice or fresh lime juice
- 1 tbsp lime zest
- ¼ tsp fine salt.
Optional Topping
- whipped cream for serving
- extra lime zest for garnish.
INSTRUCTIONS
Prepare Crust
- Heat oven to 350 F
- line a 9x13 inch pan with parchment leaving overhang and lightly grease
- mix graham cracker crumbs sugar melted butter and salt until evenly moistened
- press firmly into an even layer and bake until lightly golden about 10 to 12 minutes.
Make Filling And Bake
- Whisk condensed milk and egg yolks until smooth
- whisk in lime juice zest and salt until thickened slightly
- pour filling over hot crust and spread evenly
- bake until edges are set and center has a slight jiggle about 14 to 18 minutes
- cool at room temperature for 30 minutes.
Chill And Serve
- Refrigerate until fully cold and firm at least 2 hours or up to overnight
- lift out using parchment and slice with a warm clean knife
- serve chilled with whipped cream and extra zest if desired.
