Conversion education
File conversion concepts
Own the vocabulary of formats: encoding, codecs, containers, MIME types, lossy vs lossless, and more — then jump into converters when you are ready to act.
Basics
A file format is an agreed structure for storing digital information — bytes arranged so software knows how to read images, video, documents, or data.
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File conversion is rewriting a file from one format into another so a different app, device, or workflow can use it — ideally keeping the information you care about.
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How conversion works
Converters decode the source into an intermediate representation, then encode that into the target format — or remux compressed packets when codecs already match.
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You get a new file in a new format. Quality, size, metadata, transparency, and editability may change depending on the source/target pair and settings.
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Encoding turns raw or decoded data into a compressed or structured representation using a codec or format writer — for example raw pixels → JPG, or PCM audio → AAC.
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Decoding reads an encoded bitstream and reconstructs playable or editable data — frames, samples, or document structures — so software can display or convert them.
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Transcoding means decoding media and re-encoding it — often to a different codec, bitrate, or resolution. It is the heavy form of conversion.
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Compression reduces size. Conversion changes format. Tools often do both (PNG → smaller WebP), but you can compress within a format or convert without shrinking.
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Encoding creates a bitstream from raw/decoded data. Transcoding specifically means decoding an already-encoded file and encoding again — usually to change codec, bitrate, or size.
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Media concepts
A codec (coder-decoder) compresses and decompresses media — H.264 and HEVC for video, AAC and MP3 for audio, JPEG and AV1 stills for images.
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A container format wraps one or more media tracks (video, audio, subtitles, metadata) without being the codec itself — MP4, MKV, MOV, and WebM are containers.
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A codec compresses media; a container packages tracks. MP4 is a container; H.264 is a codec. You need both to play most videos.
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Raster images (JPG, PNG, WebP) store pixels. Vector graphics (SVG) store shapes that scale forever. Photos are raster; logos should usually be vector.
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Lossless keeps every detail (PNG, FLAC, lossless WebP). Lossy discards imperceptible data for smaller files (JPG, MP3, lossy WebP/AVIF). Choose based on master vs delivery.
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Bitrate is data per second (or per file budget). Quality is what you perceive. Higher bitrate usually helps, but codec efficiency and content complexity matter more than a single number.
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Resolution is pixel dimensions (1920×1080). File size is bytes on disk. High resolution can be small if compressed well; low resolution can be large if saved poorly.
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PPI (pixels per inch) describes pixel density for screens. DPI (dots per inch) describes printer dot density. Image files store pixel dimensions; DPI metadata is mainly a print hint.
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Files & identity
A MIME type (media type) is a standard label like image/jpeg or video/mp4 that tells browsers and servers how to treat a file’s contents.
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A file extension is the suffix after the final dot in a filename (.jpg, .docx, .mp4). It hints which program should open the file — it does not redefine the bytes inside.
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The extension is a filename hint (.jpg). The format is the real structure of the bytes (JPEG). Conversion changes the format; renaming only changes the hint.
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