Using the tool
How to compress images online
Compress one image or a mixed batch of static JPG/JPEG, PNG, WebP, AVIF, HEIC, and HEIF files directly in your browser. Use format-specific controls, adjust individual results, set a maximum Target KB, and download one file or the completed batch.
- 01
Add your images
Select or drag one or more static JPG, JPEG, PNG, WebP, AVIF, HEIC, or HEIF files into the compressor.
- 02
Compress the batch
Select Compress to process the queue locally. Automatic compression uses lightweight local image analysis to choose a suitable internal profile where that helps. JPG, PNG, WebP, and AVIF stay in their source format; HEIC and HEIF are converted to JPG.
- 03
Inspect a result
Select a completed thumbnail. Native-format results can be compared with the original, while HEIC and HEIF show the converted JPG preview instead of a fake browser comparison.
- 04
Adjust one image
Change JPEG, WebP, or AVIF quality, change the PNG colour limit, or use Target (KB) for the selected result without resetting the rest of the batch.
- 05
Set a maximum size
Enter a Target (KB) when an upload has a file-size limit. Olivez searches for the least-destructive available setting that fits at or below that maximum when the target is reachable.
- 06
Download the result
Save one completed image or select Download all to create a ZIP locally from the downloadable results.
Per-image control
Batch image compression with different settings for each image
A photograph, screenshot, logo, phone photo, and thumbnail rarely need the same compression strength just because they were selected together.
Mix supported formats in one batch
Add JPG/JPEG, PNG, WebP, AVIF, HEIC, and HEIF files together. The first pass uses the processing path for each source format rather than forcing one format or one control across the queue.
JPG/JPEG, PNG, WebP, and AVIF remain in their source format. Static HEIC and HEIF inputs are the exception: they are decoded and exported as JPG for the compressor result.
Adjust only the image that needs it
Select any completed result and change its own quality, PNG colour limit, or maximum Target (KB). Applying that change does not reset other completed results in the batch.
This makes it practical to preserve more detail in a screenshot or portrait while using stronger compression for a simpler thumbnail or background image in the same batch.
Automatic compression
Automatic compression adapts before you touch a slider
The first pass uses lightweight local image analysis to choose a measured internal profile where that improves the size-to-quality tradeoff. Manual controls remain predictable when you want to choose the setting yourself.
Content-aware JPEG and AVIF profiles
Automatic JPEG compression does not use one identical encoder recipe for every photograph, illustration, or text-heavy image. Olivez analyses bounded image statistics locally and selects from a small set of measured MozJPEG profiles, including safer handling for screenshot and text-like content.
Automatic AVIF compression can also use a more efficient internal profile for suitable structured images when the browser compute budget allows it. Manual Quality remains the value you select, and Target KB uses its own bounded search for the highest setting that fits.
Avoid lossy work when it does not help
Suitable compact PNGs can take a lossless OxiPNG-only path first. If that produces a worthwhile saving, Olivez can return the lossless result without reducing the image's RGB colours.
For normal adaptive native-format lossy compression, Olivez can also keep the untouched original when the re-encoded file saves only a trivial amount. Manual adjustments and Target KB are not silently replaced by this optimisation.
Maximum file size
Compress an image to 50 KB, 100 KB, 200 KB, or any target size
Use Target (KB) when a form, CMS, application portal, email workflow, or other upload requires the image to stay under a maximum file size. Enter the ceiling the destination actually gives you instead of repeatedly guessing with a quality slider.
Reduce image size in KB without guessing quality
Enter the maximum size you need for the selected result. Olivez searches the available encoder settings for the least-destructive setting it can find that stays at or below that limit.
For JPEG, WebP, and AVIF, that means finding the highest usable quality. For PNG, it means finding the highest colour count that fits. The pixel dimensions are not reduced to force the target.
The same control works for a 20 KB, 50 KB, 100 KB, 200 KB, 500 KB, or another maximum. You do not need a separate compressor for each fixed number.
What happens when the target cannot be reached
A maximum is not an exact-byte guarantee. Some images simply cannot become small enough with the available compression range while keeping the same pixel dimensions and native format.
For JPG/JPEG, PNG, WebP, and AVIF, Olivez keeps the original available rather than resizing the image or silently converting it just to manufacture a passing number.
HEIC and HEIF are different because the compressor output must be JPG. If even the strongest available JPEG compression is still above the requested maximum, the best-effort JPG remains downloadable and the result clearly reports that the target was missed.
Use the upload limit you were actually given
If a destination says “maximum 100 KB”, enter 100. If it allows 200 KB, there is usually no reason to force the image down to 50 KB and sacrifice more detail than the upload rule requires.
Target KB is deliberately a ceiling. The result may land below the number because encoder settings are discrete; Olivez does not pad or enlarge the file just to manufacture an exact byte count.
Target KB keeps dimensions unchanged
Olivez searches compression settings rather than silently shrinking pixel dimensions. That matters when an upload requirement specifies file size but you still need the original width and height.
If a native-format image cannot reach the requested maximum through the available compression range, the tool reports the target as unreachable instead of resizing or changing format behind your back.
If the source already fits
For JPG/JPEG, PNG, WebP, and AVIF, an original file that is already at or below the requested maximum can be kept as-is. That avoids unnecessary lossy re-encoding just to produce a second file with the same job to do.
HEIC and HEIF do not take that shortcut because their compressor result is intentionally JPG, even when the original HEIC file was already smaller than the chosen target.
Manual adjustment
Recommended manual image compression settings
Automatic compression adapts internal profiles to the image where that helps. Use these values when you choose to adjust a completed result manually; Quality or Colors remains the value you select, and the real output should still be inspected.
| Image type | Start with | What to inspect |
|---|---|---|
| JPEG photograph | Quality 80 | Inspect faces, fine textures, text, and high-contrast edges. |
| JPEG thumbnail | Quality 65–75 | Lower settings may work when the image will only be displayed at a small size. |
| PNG screenshot | 128–256 colours | Increase the limit when small text, shadows, gradients, or syntax colours change visibly. |
| PNG logo or icon | 32–128 colours | Flat graphics can often use fewer colours than screenshots or illustrations. |
| PNG with gradients | 256 colours | Use a higher limit when banding appears. A different format may suit photographic gradients better. |
| WebP photograph | Quality 75–85 | Reduce the value gradually while checking texture, faces, text, and smooth colour transitions. |
| AVIF photograph | Quality 45–60 | Start near 50, then compare fine texture and smooth gradients before reducing it further. |
Formats
How JPG, PNG, WebP, AVIF, HEIC, and HEIF are handled
The compressor does not pretend every image format behaves the same. Each supported format uses a processing path suited to the implemented codec, and HEIC/HEIF has different output semantics from the native-format inputs.
JPEG compression
Quality 1–100 · Target KB
JPEG is best suited to photographs and other images with continuous colour variation. It does not support transparency and can create visible artefacts around text, interface elements, and high-contrast edges.
Olivez decodes the source and re-encodes it with MozJPEG. In automatic mode, bounded local image analysis can select a measured JPEG profile with different internal chroma handling, subsampling, and a conservative effective-quality adjustment when that improves the size-to-quality tradeoff. Text and screenshot-like content stays on the safer profile.
Manual Quality remains the value you choose. If you adjust JPEG yourself, quality 80 is a practical starting point, not an “80% quality” promise or a guaranteed file size. Target KB instead searches for the highest available quality that fits the requested ceiling.
PNG colour reduction
2–256 colours · Target KB
PNG works well for screenshots, text, diagrams, logos, icons, and graphics that require transparency. These images often contain fewer meaningful colours than photographs.
In automatic mode, suitable compact PNGs can first try an OxiPNG-only optimisation. When that lossless pass produces a worthwhile result, the RGB pixels do not need to be colour-reduced at all. The lossless-first attempt is intentionally bounded because aggressive OxiPNG work on larger images can be slow in a browser.
When colour reduction is used, the control limits the RGB colours retained in the processed image. Fewer colours can reduce flat artwork dramatically, while gradients, shadows, anti-aliased edges, and screenshots may show banding or colour changes.
Alpha values remain while RGB colours are reduced. OxiPNG then performs a lossless optimisation pass on that colour-reduced PNG. OxiPNG does not restore colours removed by the earlier lossy step. Manual Colors mode uses this explicit colour-reduction path rather than the automatic lossless-first shortcut.
WebP compression
Quality 1–100 · Target KB
WebP is useful for modern web photographs and graphics and can retain static transparency. This compressor uses lossy libwebp encoding for the image data.
Higher values preserve more texture and colour detail. Lower values normally create smaller files but may introduce smoothing or compression artefacts.
A WebP quality value is not directly equivalent to the same JPEG quality number. Compare the output instead of matching the numbers across formats.
On browsers that support WebAssembly SIMD, Olivez loads a SIMD WebP encoder build for faster processing and falls back to the scalar encoder when needed. The measured SIMD path produced identical WebP bytes to the scalar path; it changes execution speed rather than the chosen compression result.
AVIF compression
Quality 1–100 · Target KB
Static AVIF images remain AVIF. Olivez decodes the image and re-encodes it as lossy 8-bit AVIF at the selected quality while keeping the decoded pixel dimensions.
Automatic compression can use a more efficient higher-effort AVIF profile for suitable structured images when the image size, batch size, and operation keep the compute cost reasonable. Large images, larger batches, manual controls, and Target KB stay on the faster conservative profile.
Start near quality 50 and inspect fine texture, faces, text, and smooth gradients before reducing it further. AVIF quality numbers are encoder settings rather than equivalents of JPEG or WebP quality values.
Do not rely on this re-encoding path to preserve every advanced source characteristic. Higher bit depth, HDR-related information, metadata, and embedded colour profiles should not be assumed to survive a newly encoded result.
HEIC and HEIF to JPG
Converted JPG · Target KB
Static HEIC and HEIF inputs are decoded locally and converted to JPEG rather than being returned as HEIC/HEIF. The conversion uses the designated primary still image and MozJPEG for the JPG output.
JPEG does not support transparency, so any decoded alpha is flattened against white before encoding. HEIC/HEIF image sequences are rejected instead of being silently reduced to one frame.
The initial compression pass creates the JPG result. In the result controls, HEIC/HEIF opens on Target (KB) rather than showing a separate manual JPEG-quality slider.
| Input | Output | Control | Method |
|---|---|---|---|
| JPG / JPEG | JPG / JPEG | Quality 1–100 or Target KB | Adaptive MozJPEG re-encoding; manual Quality stays exact |
| PNG | PNG | 2–256 colours or Target KB | Lossless OxiPNG when worthwhile; otherwise colour reduction + OxiPNG |
| WebP | WebP | Quality 1–100 or Target KB | Lossy libwebp re-encoding |
| AVIF | AVIF | Quality 1–100 or Target KB | Adaptive lossy 8-bit AVIF re-encoding |
| HEIC / HEIF | JPG | Target KB after conversion | Local HEIF decoding, then lossy MozJPEG encoding |
Review the result
Compare original and compressed images before downloading
Compression is a tradeoff. File-size savings matter only if the visual result is still acceptable for the image's real use.
Use the comparison where the browser can render both sides
For JPG/JPEG, PNG, WebP, and AVIF, the comparison panel places the source and the downloadable result on opposite sides of a movable divider.
Drag across faces, hair, fine textures, small text, gradients, shadows, and transparent edges. Also check the image near its intended display size; a defect that looks dramatic while zoomed in may be irrelevant in a thumbnail, while damaged small text can matter immediately.
Why HEIC and HEIF show a converted preview instead
Browser-native HEIC rendering cannot be assumed. Showing a fake “original” side would make the comparison misleading.
HEIC/HEIF results therefore show the actual converted JPG preview, its file-size change, and Target (KB) controls. The UI reflects what the browser can truthfully display rather than pretending all formats have identical preview support.
Why an image may barely shrink
The source may already be efficiently compressed. Re-encoding an optimised JPEG, PNG, WebP, or AVIF does not guarantee another large reduction.
High JPEG, WebP, or AVIF quality retains more information. A PNG colour limit close to the image's existing colour range may also produce only modest savings.
Small files contain less removable data, while photographs stored as PNG often remain large because PNG is generally less efficient for continuous-tone photography than a photographic codec.
What happens when re-encoding is not worth it
For same-format JPG/JPEG, PNG, WebP, and AVIF compression, Olivez compares the generated byte size with the source instead of assuming that re-encoding must be better.
In normal adaptive native-format lossy compression, Olivez also keeps the original when the new file saves less than both 1 KiB and 2%. This conservative rule avoids another lossy generation for a negligible gain. A result that is equal to or larger than the source is likewise discarded.
Manual adjustments and Target KB bypass the trivial-saving rule because the user explicitly requested that operation. HEIC and HEIF are also different because conversion to JPG is part of that workflow, so the converted JPG remains the result even when it is larger than the HEIC/HEIF source.
File handling
Compress images privately without uploading the files
Image bytes stay in the browser
Selected files are read through browser APIs and passed to a dedicated image-compression worker. The codecs run locally using JavaScript and WebAssembly assets.
Image bytes are not submitted to a server-side compression endpoint. ZIP creation also happens locally when Download all is requested.
Automatic compression also computes a bounded set of image statistics locally to choose internal encoder profiles. Those content-analysis signals are used inside the browser worker rather than being uploaded for remote analysis.
This describes the handling of your selected image data. The web page and codec assets still need to be loaded by the browser like any other web application.
Metadata and colour information
Creating a new encoded image may omit EXIF camera details, GPS coordinates, embedded thumbnails, comments, editing data, and colour profiles.
When Olivez keeps an untouched original because a normal re-encoding did not help—or because that native-format source already fits a target—the original bytes and their metadata remain unchanged.
Keep a separate source when metadata, colour-management behaviour, editing history, or evidence provenance matters. Do not use general image compression as a dedicated metadata-scrubbing guarantee.
Safeguards
File limits and current limitations
These documented safeguards keep browser memory use more predictable on large files and batches. A particular browser or device can still reach its practical memory limit sooner.
- Images per batch
- 40
- Maximum file size
- 50 MiB
- Maximum batch size
- 250 MiB
- Maximum resolution
- 80 megapixels
Images are processed sequentially through one worker to reduce peak browser memory use. A particular browser or device can still run out of memory below the documented limits.
- Only static JPG/JPEG, PNG, WebP, AVIF, HEIC, and HEIF inputs are supported.
- Animated PNG, animated WebP, animated AVIF, and HEIC/HEIF image sequences are rejected rather than silently flattened into one frame.
- GIF, SVG, BMP, TIFF, ICO, PDF, and other unsupported file types are not accepted by this compressor.
- JPG/JPEG, PNG, WebP, and AVIF outputs keep their source format. HEIC and HEIF are the exception and are converted to JPG.
- The compressor does not resize, crop, or provide a manual rotation tool. Target KB works through compression settings rather than changing pixel dimensions.
- Target KB is a maximum-size goal, not an exact-byte guarantee. Some images cannot reach a requested maximum without resizing or changing format.
- JPEG, WebP, AVIF, and HEIC/HEIF-to-JPG encoding is lossy and can alter fine detail.
- Automatic PNG compression may return a lossless OxiPNG-only result when that produces a worthwhile saving; otherwise RGB colour reduction is lossy and the OxiPNG pass after it is lossless relative to the colour-reduced image.
- In normal adaptive native-format lossy compression, Olivez may keep the original when re-encoding saves only a trivial amount. Manual adjustments and Target KB are not overridden by that retention rule.
- Re-encoding may remove metadata, embedded thumbnails, and colour-profile information.
- Browser memory and device performance can impose a lower practical limit than the documented safeguards.
Common questions
Image compressor FAQ
Is this image compressor free and does it require an account?
Yes. Compression, per-image adjustment, Target KB, comparison, individual downloads, and ZIP export are free and do not require an account. Olivez does not add a watermark; the documented file and browser-safety limits still apply.
Are my images uploaded to a compression server?
No. The selected image bytes are read and processed in the current browser tab. Compression and ZIP creation run locally rather than sending the files to a server-side compression endpoint.
Which image formats are supported?
Static JPG/JPEG, PNG, WebP, AVIF, HEIC, and HEIF inputs are supported. JPG/JPEG, PNG, WebP, and AVIF remain in their format; HEIC and HEIF are converted to JPG.
Can I compress an image under 50 KB, 100 KB, 200 KB, or another limit?
Yes. Select a completed image, open Target (KB), and enter the maximum size you need. Olivez searches for the least-destructive available encoder setting that fits at or below that maximum when the target is reachable. The result may be smaller than the number because Target KB is a ceiling, not padding to an exact byte count.
Does Target KB make the image exactly that size?
No. The number is treated as a maximum, not an exact-byte promise. If a smaller result can be produced without resizing, Olivez keeps the highest available quality or PNG colour count it finds that still fits the limit.
How do I reduce image size in KB without resizing?
Use Target (KB) on the selected result and enter the maximum allowed by the destination. Olivez changes compression settings rather than pixel dimensions. If a native-format image cannot reach the requested ceiling without resizing or format conversion, the tool reports that limitation instead of silently changing the dimensions.
What happens if the target size cannot be reached?
For JPG/JPEG, PNG, WebP, and AVIF, Olivez does not resize or silently change format just to force the target. When the target is unreachable, the original remains available. HEIC and HEIF must become JPG, so the compressor keeps the strongest best-effort JPG and clearly reports when that JPG is still above the requested maximum.
What if the original image already fits my Target KB?
For JPG/JPEG, PNG, WebP, and AVIF, the original can be kept instead of needlessly re-encoding a file that already meets the maximum. HEIC and HEIF are different because their downloadable compressor result is JPG.
Can I use different compression settings for each image in one batch?
Yes. Compress the batch, select any completed result, and change only that image. JPEG, WebP, and AVIF use quality controls, PNG uses a colour limit, and completed images can also use their own Target KB. Other completed results remain unchanged.
Can one batch mix JPG, PNG, WebP, AVIF, HEIC, and HEIF files?
Yes. A batch can mix the supported static formats up to the documented limits. Each image follows the processing path appropriate to its format, and HEIC/HEIF results are downloaded as JPG.
Does the compressor resize images?
No. Compression and Target KB do not deliberately change pixel width or height. If an upload limit cannot be reached without resizing, the tool reports that limitation instead of silently changing the dimensions.
What happens to HEIC or HEIF files?
Static HEIC and HEIF images are decoded locally and converted to JPG with MozJPEG. After conversion, the result view focuses on Target KB rather than exposing a separate manual JPEG-quality control.
Why is there no normal before-and-after slider for HEIC or HEIF?
Browser-native HEIC display cannot be assumed. Olivez therefore shows the real converted JPG preview instead of pretending that the browser can reliably render the original HEIC side of a comparison.
Is HEIC transparency preserved in the JPG?
No. JPEG does not support transparency. Any decoded transparent pixels are flattened against white before the JPG is encoded.
How does automatic image compression choose settings?
The browser computes a bounded set of local image statistics such as colour diversity, tonal variation, edges, flat regions, transparency, and texture or noise. Olivez uses those signals to choose from a small set of measured internal profiles where adaptive encoding helps. This analysis stays in the browser, and manual Quality or Colors controls remain explicit when you choose them.
What JPEG, WebP, or AVIF quality should I use?
Automatic compression can adapt internal JPEG and AVIF profiles to image characteristics, so you do not need one universal quality number for every file. If you adjust a result manually, use the suggested values only as starting points: manual Quality remains the value you select, and quality numbers are not directly equivalent across JPEG, WebP, and AVIF.
What does the PNG colour control do?
It limits the RGB colours retained in the processed PNG from 2 through 256. Fewer colours can reduce file size substantially for flat artwork, but gradients, shadows, anti-aliased edges, or screenshots may show visible changes.
Is PNG compression lossless?
It can be for some automatic results. Suitable compact PNGs may first use an OxiPNG-only pass that changes the representation without changing the image pixels. If that lossless result is not useful enough, the normal PNG path may reduce RGB colours, which is lossy, and then apply OxiPNG losslessly to the colour-reduced result. Manual Colors mode uses the explicit colour-reduction path.
What happens when normal compression saves almost nothing or creates a larger file?
For normal adaptive same-format compression, Olivez can keep the untouched original when a lossy re-encode saves only a trivial amount, and it also keeps the original when the generated result is equal to or larger than the source. Manual adjustments and Target KB still honour the requested operation. HEIC/HEIF conversion is different because the required output is JPG.
Can I compress an image without losing quality?
No lossy compressor can guarantee an unchanged image. JPEG, WebP, AVIF, and HEIC/HEIF-to-JPG encoding can alter detail, while PNG colour reduction can change RGB values. Use the comparison where available and keep the original until the result is acceptable.
Can compression remove EXIF, GPS, or colour-profile information?
Yes. A newly encoded result may omit EXIF, GPS, camera, thumbnail, comment, editing, and colour-profile information. When Olivez keeps an untouched original instead of re-encoding it, the original bytes and metadata remain unchanged.
How does Download all work?
The browser creates a ZIP locally from the completed downloadable results. Duplicate output names receive numeric suffixes so files do not overwrite one another inside the archive.
Technical references
Primary documentation for the formats and codecs used by the compressor.