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Encoders and decoders

Base64 Decoder / Encoder

Decode Base64 to readable text or a downloadable file, or encode text to Base64.

  • Runs in your browser
  • Instant results
  • Free, no sign-up
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How to use the Base64 Decoder

  1. Paste the Base64 string (data URLs work too).
  2. Read the decoded text, or download it if it is a file such as an image.
  3. Switch to Encode to turn text into Base64.

Frequently asked questions

What is Base64URL?

A variant that uses - and _ instead of + and / and drops padding, so it is safe in URLs and JWTs. Both variants are decoded automatically.

Why does the decoded text look broken?

The data is probably binary, such as an image or compressed file. Use the download button instead.

Is Base64 encryption?

No. It is only an encoding; anyone can decode it, so never use it to protect secrets.

URL DecoderDecode and encode URLs and query strings with percent encoding. See the URL broken into host, path and parameters. Handles double-encoded text. JWT DecoderDecode JWT header and payload, read claim dates like exp and iat, check expiry, and verify HS256/HS384/HS512 signatures. Your token stays in your browser. Unicode ConverterConvert text to Unicode code points, JavaScript, Python, HTML and CSS escapes, and UTF-8 bytes, or decode escapes back to text. Shows each character.

Practice Python with coding challenges

Solve hands-on problems right in this editor: run the sample tests, submit, and get an AI code review.

All Python challenges
Easy

Average of Three

Average three whole numbers.

You'll learn ArithmeticDivision
BeginnerLearning-pathVariables
Python C++ C#
1 solved
View solutions (1)
Easy

Rectangle Perimeter

Compute the perimeter of a rectangle from its sides.

You'll learn ArithmeticReturn values
BeginnerLearning-pathVariables
Python C++ C#
1 solved
View solutions (1)
Medium

One Generation of a Genetic Algorithm

Breed the next generation of bit strings with tournament selection, single-point crossover and mutation.

You'll learn Genetic algorithmsEvolutionary search
OptimizationSimulationai
Python C++ C#
0 solved
No solutions yet
Easy

Epsilon-Greedy Multi-Armed Bandit

Balance exploration and exploitation on a multi-armed bandit with epsilon-greedy action selection.

You'll learn Explore vs exploitBandits
Reinforcement learningaimachine learning
Python C++ C#
0 solved
No solutions yet
Easy

Markov Chain State Distribution

Propagate a probability distribution through a Markov chain's transition matrix for a number of steps.

You'll learn Markov chainsProbability
Simulationaimath
Python C++ C#
0 solved
No solutions yet
Medium

Value Iteration

Compute how valuable each state of a Markov decision process is by repeatedly applying the Bellman optimality update.

You'll learn Bellman equationMDPs
Reinforcement learningaimachine learning
Python C++ C#
0 solved
No solutions yet
Medium

Q-Learning Updates

Apply the Q-learning update to a stream of experiences and watch rewards flow back to earlier states.

You'll learn Q-learningDiscounted rewards
Reinforcement learningaimachine learning
Python C++ C#
0 solved
No solutions yet
Medium

Alpha-Beta Pruning

Evaluate a game tree with minimax and alpha-beta pruning, and count how many leaves the search really looks at.

You'll learn Alpha-beta pruningGame search
RecursionTreesai
Python C++ C#
0 solved
No solutions yet
Medium

Minimax Tic-Tac-Toe

Pick the perfect tic-tac-toe move by searching the whole game tree with minimax.

You'll learn MinimaxGame trees
Recursionai
Python C++ C#
0 solved
No solutions yet
Medium

A* Search on a Weighted Grid

Find the cheapest path across a grid of terrain costs with A*, the search algorithm behind game and robot pathfinding.

You'll learn A* searchHeuristics
GraphsGridsShortest-pathai
Python C++ C#
0 solved
No solutions yet
Medium

Temperature and Top-K Sampling

Choose the next token like a language model does: keep the top k logits, apply temperature, and sample.

You'll learn Text generationSampling
aimachine learning
Python C++ C#
0 solved
No solutions yet
Hard

Multi-Head Self-Attention

Project the input into queries, keys and values, run attention in several heads in parallel, and combine them.

You'll learn Multi-head attentionMatrix projections
aimachine learning
Python C++ C#
0 solved
No solutions yet